Abstract: The mechanosensitive channel MscL of the plasma membrane of bacteria is a homopentamer involved in the protection of cells during osmotic downshock. The MscL protein, a polypeptide of 136 residues, was recently shown to require YidC to be inserted in the inner membrane of E. coli. The insertase YidC is a component of an insertion pathway conserved in bacteria, mitochondria and chloroplasts. MscL insertion was independent of the Sec translocon. Here, we report sucrose gradient centrifugation and freeze-etching microscopy experiments showing that MscL produced in a cell-free system complemented with preformed liposomes is able to insert directly in a pure lipid bilayer. Patch-clamp experiments performed with the resulting proteoliposomes showed that the protein was highly active. In vitro cell-free synthesis targeting to liposomes is a new promising expression system for membrane proteins, including those that might require an insertion machinery in vivo. Our results also question the real role of insertases such as YidC for membrane protein insertion in vivo.
Abstract: Corynebacterineae are gram-positive bacteria that possess a true outer membrane composed of mycolic acids and other lipids. Little is known concerning the modulation of mycolic acid composition and content in response to changes in the bacterial environment, especially temperature variations. To address this question, we investigated the function of the Rv3802c gene, a gene conserved in Corynebacterineae and located within a gene cluster involved in mycolic acid biosynthesis. We showed that the Rv3802 ortholog is essential in Mycobacterium smegmatis, while its Corynebacterium glutamicum ortholog, NCgl2775, is not. We provided evidence that the NCgl2775 gene is transcriptionally induced under heat stress conditions, and while the corresponding protein has no detectable activity under normal growth conditions, the increase in its expression triggers an increase in mycolic acid biosynthesis concomitant with a decrease in phospholipid content. We demonstrated that these lipid modifications are part of a larger outer membrane remodeling that occurs in response to exposure to a moderately elevated temperature (42 degrees C). In addition to showing an increase in the ratio of saturated corynomycolates to unsaturated corynomycolates, our results strongly suggested that the balance between mycolic acids and phospholipids is modified inside the outer membrane following a heat challenge. Furthermore, we showed that these lipid modifications help the bacteria to protect against heat damage. The NCgl2775 protein and its orthologs thus appear to be a protein family that plays a role in the regulation of the outer membrane lipid composition of Corynebacterineae under stress conditions. We therefore propose to name this protein family the envelope lipids regulation factor (ElrF) family.
Abstract: Synthesis of the Klebsiella oxytoca outer membrane secretin PulD, or its membrane-associated core domain, in a liposome-supplemented Escherichia coli in vitro transcription-translation system resulted in the formation of multimers that appeared as typical dodecameric secretin rings when examined by negative-stain electron microscopy. Cryo-electron microscopy of unstained liposomes and differential extraction by urea indicated that the secretin particles were inserted into the liposome membranes. When made in the presence of the detergent Brij-35, PulD and the core domain were synthesized as monomers. Both proteins caused almost immediate growth cessation when synthesized in E. coli without a signal peptide. The small amounts of PulD synthesized before cell death appeared as multimers with characteristics similar to those of the normal outer membrane secretin dodecamers. It was concluded that multimerization and membrane insertion are intrinsic properties of secretin PulD that are independent of a specific membrane environment or membrane-associated factors. The closely related Erwinia chrysanthemi secretin OutD behaved similarly to PulD in all assays, but the more distantly related Neisseria meningitidis secretin PilQ did not form multimers either when made in vitro in the presence of liposomes or when made in E. coli without its signal peptide. This is the first report of the apparently spontaneous in vitro assembly and membrane insertion of a large outer membrane protein complex. Spontaneous multimerization and insertion appear to be restricted to outer membrane proteins closely related to PulD.
Abstract: Secretins are a unique class of bacterial multimeric outer membrane proteins that probably differ considerably from other, less complex outer membrane proteins in their overall structure and organization, and in their requirements for outer membrane targeting and assembly factors. In this MicroCommentary, we discuss these differences with respect to the role of a specific class of lipoproteins, often referred to as pilotins, in secretin complex assembly. We compare them with other lipoproteins that play a role in Omp85/YaeT-mediated assembly of more classical outer membrane proteins. One of the examples we have chosen is the Myxococcus Xanthus lipoprotein Tgl. Coculture of cells with and without Tgl allows secretin assembly (and, hence, type IV pilus assembly) in the cells without Tgl, indicating that it can act by cell-to-cell contact or can transfer between cells.
Abstract: Dodecamerization and insertion of the outer membrane secretin PulD is entirely determined by the C-terminal half of the polypeptide (PulD-CS). In the absence of its cognate chaperone PulS, PulD-CS and PulD mislocalize to the inner membrane, from which they are extractable with detergents but not urea. Electron microscopy of PulD-CS purified from the inner membrane revealed apparently normal dodecameric complexes. Electron microscopy of PulD-CS and PulD in inner membrane vesicles revealed inserted secretin complexes. Mislocalization of PulD or PulD-CS to this membrane induces the phage shock response, probably as a result of a decreased membrane electrochemical potential. Production of PulD in the absence of the phage shock response protein PspA and PulS caused a substantial drop in membrane potential and was lethal. Thus, PulD-CS and PulD assemble in the inner membrane if they do not associate with PulS. We propose that PulS prevents premature multimerization of PulD and accompanies it through the periplasm to the outer membrane. PulD is the first bacterial outer membrane protein with demonstrated ability to insert efficiently into the inner membrane.
Abstract: Limited proteolysis, secondary structure and biochemical analyses, mass spectrometry, and mass measurements by scanning transmission electron microscopy were combined with cryo-electron microscopy to generate a three-dimensional model of the homomultimeric complex formed by the outer membrane secretin PulD, an essential channel-forming component of the type II secretion system from Klebsiella oxytoca. The complex is a dodecameric structure composed of two rings that sandwich a closed disc. The two rings form chambers on either side of a central plug that is part of the middle disc. The PulD polypeptide comprises two major, structurally quite distinct domains; an N domain, which forms the walls of one of the chambers, and a trypsin-resistant C domain, which contributes to the outer chamber, the central disc, and the plug. The C domain contains a lower proportion of potentially transmembrane beta-structure than classical outer membrane proteins, suggesting that only a small part of it is embedded within the outer membrane. Indeed, the C domain probably extends well beyond the confines of the outer membrane bilayer, forming a centrally plugged channel that penetrates both the peptidoglycan on the periplasmic side and the lipopolysaccharide and capsule layers on the cell surface. The inner chamber is proposed to constitute a docking site for the secreted exoprotein pullulanase, whereas the outer chamber could allow displacement of the plug to open the channel and permit the exoprotein to escape.
Abstract: Corynebacteria belong to a distinct Gram-positive group of bacteria including mycobacteria and nocardia, which are characterized by the presence of mycolic acids in their cell wall. These bacteria share the property of having an unusual cell envelope structural organization close to Gram-negative bacteria. In addition to the inner membrane, the cell envelope is constituted of a thick arabinogalactan-peptidoglycan polymer covalently linked to an outer lipid layer, which is mainly composed of mycolic acids and probably organized in an outer membrane like structure. In some species, the cell is covered by a crystalline surface layer composed of a single protein species, which is anchored in the outer membrane like barrier. An increasing number of reports have led to a better understanding of the structure of the cell wall of Corynebacterium glutamicum. These works included the characterization of several cell wall proteins like S-layer protein and porins, genetic and biochemical characterization of mycolic acids biosynthesis, ultrastructural description of the cell envelope, and chemical analysis of its constituents. All these data address new aspects regarding cell wall permeability towards macromolecules and amino acids but also open new opportunities for biotechnology applications.
Abstract: Vesicles consisting of pure trehalose dicorynomycolate (TDCM), the corynebacterial analog of the most studied mycobacterial glycolipid 'cord factor', were isolated from Corynebacterium glutamicum cells by mild detergent treatment; these induced in vivo a macrophage priming similar to that obtained with mycobacterial-derived trehalose dimycolate. In vitro, both TDCM and bacterial lipopolysaccharide (LPS) induced in macrophages the production of nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha), endotoxin tolerance, and were primed for an enhanced secondary NO response to LPS. Interferon-gamma pretreatment did not influence the LPS-induced TNF-alpha response, but considerably increased the TDCM-induced response.
Abstract: Corynebacteria are Gram-positive bacteria with a very peculiar cell envelope structure as it is constituted of an inner membrane and an outer membrane-like structure. Protein secretion in Corynebacterium glutamicum was studied in vivo, using the S-layer protein PS2 as a model. We show that different variants of PS2 protein are exported through the whole cell envelope with a half-life ranging between 2 and 4 min, by a two-step mechanism. The first step, which is over after about 1.5 min, is ATP- and proton motive force-dependent and may correspond to translocation across the inner membrane via the 'Sec' machinery. The second step, across the cell wall and the outer mycolate layer, is rapid but independent of energy sources. This very efficient secretion process across the mycolate layer raises the question of the existence in this layer of a specific machinery.
Abstract: PS1 is a major exported protein of Corynebacterium glutamicum homologous to mycobacterial antigen 85. It is largely associated with the mycolic acid-containing cell wall and acts as a mycoloyl transferase. The transport of PS1 to the cell wall is slow and occurs through two energetically distinct steps: the first one, which includes processing by signal peptidase, is rapid and inhibited by sodium azide or carbonyl cyanide m-chlorophenylhydrazone. This step is probably associated with translocation across the cytoplasmic membrane. The kinetics of the second step depend on the size of the polypeptide chain to be transported but neither ATP nor proton motive force is required. This step may correspond to the diffusion of PS1 across the cell wall to its final location.
Abstract: With the recent success of the heterologous expression of mycobacterial antigens in corynebacteria, in addition to the importance of these bacteria in biotechnology and medicine, a better understanding of the structure of their cell envelopes was needed. A combination of molecular compositional analysis, ultrastructural appearance and freeze-etch electron microscopy study was used to arrive at a chemical model, unique to corynebacteria but consistent with their phylogenetic relatedness to mycobacteria and other members of the distinctive suprageneric actinomycete taxon. Transmission electron microscopy and chemical analyses showed that the cell envelopes of the representative strains of corynebacteria examined consisted of (i) an outer layer composed of polysaccharides (primarily a high-molecular-mass glucan and arabinomannans), proteins, which include the mycoloyltransferase PS1, and lipids; (ii) a cell wall glycan core of peptidoglycan-arabinogalactan which may contain other sugar residues and was usually esterified by corynomycolic acids; and (iii) a typical plasma membrane bilayer. Freeze-etch electron microscopy showed that most corynomycolate-containing strains exhibited a main fracture plane in their cell wall and contained low-molecular-mass porins, while the fracture occurred within the plasma membrane of strains devoid of both corynomycolate and pore-forming proteins. Importantly, in most strains, the amount of cell wall-linked corynomycolates was not sufficient to cover the bacterial surface; interestingly, the occurrence of a cell wall fracture plane correlated with the amount of non-covalently bound lipids of the strains. Furthermore, these lipids were shown to spontaneously form liposomes, indicating that they may participate in a bilayer structure. Altogether, the data suggested that the cell wall permeability barrier in corynebacteria involved both covalently linked corynomycolates and non-covalently bound lipids of their cell envelopes.
Abstract: When expressed in Escherichia coli, the 15 Klebsiella oxytoca pul genes that encode the so-called Pul secreton or type II secretion machinery promote pullulanase secretion and the assembly of one of the secreton components, PulG, into pili. Besides these pul genes, efficient pullulanase secretion also requires the host dsbA gene, encoding a periplasmic disulfide oxidoreductase, independently of disulfide bond formation in pullulanase itself. Two secreton components, the secretin pilot protein PulS and the minor pseudopilin PulK, were each shown to posses an intramolecular disulfide bond whose formation was catalyzed by DsbA. PulS was apparently destabilized by the absence of its disulfide bond, whereas PulK stability was not dramatically affected either by a dsbA mutation or by the removal of one of its cysteines. The pullulanase secretion defect in a dsbA mutant was rectified by overproduction of PulK, indicating reduced disulfide bond formation in PulK as the major cause of the secretion defect under the conditions tested (in which PulS is probably present in considerable excess of requirements). PulG pilus formation was independent of DsbA, probably because PulK is not needed for piliation.
Abstract: Mycolic acids, long-chain (C70-C90) alpha-alkyl, beta-hydroxy fatty acids, are characteristic cell envelope components of mycobacteria; similar but shorter-chain substances occur in corynebacteria and related taxa. These compounds apparently play an important role in the physiology of these bacteria. The deduced N-terminal region of PS1, one of the two major secreted proteins of Corynebacterium glutamicum encoded by the csp1 gene, is similar to the antigens 85 complex of Mycobacterium tuberculosis which has been shown to be associated in vitro with a mycoloyltransferase activity onto trehalose. Overexpression of PS1 in the wild-type strain of C. glutamicum suggested the implication of the protein in the transfer of corynomycolates, evidenced by an increase esterification of the cell wall arabinogalactan with corynomycolic acid residues and an accumulation of trehalose dicorynomycolates. Overexpression of truncated forms of PS1 demonstrated that the crucial region for transfer activity of the protein involves all the region of homology with antigens 85. To establish the putative mycoloyltransferase activity of PS1, a csp1-inactivated mutant of C. glutamicum was biochemically characterized. Inactivation of the gene resulted in: (i) a 50% decrease in the cell wall corynomycolate content; (ii) the alteration of the permeability of the C. glutamicum cell envelope; (iii) the decrease of the trehalose dicorynomycolate content; (iv) the accumulation of trehalose monocorynomycolate; and (v) the appearance of a glycolipid identified as 6-corynomycoloylglucose. Complementation of the mutant by the csp1 gene fully restored the wild-type phenotype. Finally, a mycoloyltransferase assay established that PS1 possesses a trehalose mycoloyltransferase activity. To define the in vivo function of antigens 85, the csp1-inactivated mutant was complemented with the fbpA, fbpB or fbpC genes. Complementation with the different fbp genes restored the normal cell wall corynomycolate content and permeability, but did not affect either the fate of trehalose corynomycolates or the occurrence of glucose corynomycolate. Thus, PS1 is one of the enzymes that transfer corynomycoloyl residues onto both the cell wall arabinogalactan and trehalose monocorynomycolate, whereas in the whole bacterium the mycobacterial antigens 85A, 85B and 85C can transfer mycolates only onto the cell wall acceptor in C. glutamicum.
Abstract: Three strains of Corynebacterium producing various amounts of PS2 S-layer protein were studied. For all strains, more PS2 was produced if the bacteria were grown in minimal medium supplemented with lactate than if they were grown in minimal medium supplemented with glucose. The consumption of substrate and PS2 production was studied in cultures with mixed carbon sources. It was found that the inhibitory effect of glucose consumption was stronger than the stimulatory effect of lactate in one strain, but not in the other two strains. The regulation of gene expression involved in S-layer formation may involve metabolic pathways, which probably differ between strains. S-layer organization was also studied by freeze-fracture electron microscopy. It was found that low levels of PS2 production correlated with the partial covering of the cell surface by a crystalline array. Finally, it was found that PS2 production was mainly regulated by changes in gene expression and that secretion was probably not a limiting step in PS2 accumulation.
Abstract: In this chapter we report on the molecular biology of crystalline surface layers of different bacterial groups. The limited information indicates that there are many variations on a common theme. Sequence variety, antigenic diversity, gene expression, rearrangements, influence of environmental factors and applied aspects are addressed. There is considerable variety in the S-layer composition, which was elucidated by sequence analysis of the corresponding genes. In Corynebacterium glutamicum one major cell wall protein is responsible for the formation of a highly ordered, hexagonal array. In contrast, two abundant surface proteins from the S-layer of Bacillus anthracis. Each protein possesses three S-layer homology motifs and one protein could be a virulence factor. The antigenic diversity and ABC transporters are important features, which have been studied in methanogenic archaea. The expression of the S-layer components is controlled by three genes in the case of Thermus thermophilus. One has repressor activity on the S-layer gene promoter, the second codes for the S-layer protein. The rearrangement by reciprocal recombination was investigated in Campylobacter fetus. 7-8 S-layer proteins with a high degree of homology at the 5' and 3' ends were found. Environmental changes influence the surface properties of Bacillus stearothermophilus. Depending on oxygen supply, this species produces different S-layer proteins. Finally, the molecular bases for some applications are discussed. Recombinant S-layer fusion proteins have been designed for biotechnology.
Abstract: PS2 is the S-layer protein of Corynebacterium glutamicum. The S-layer may be detached from the cell as organized sheets by detergents at room temperature. The solubilization of PS2 in the form of monomers requires detergent treatment at high temperature (70 degrees C), conditions under which the protein is denatured. Treatment of the cells with proteinase K or trypsin results in the detachment of the organized S-layer, which remains organized. Because we show that trypsin cleaves the C-terminal part of the protein, we conclude that this domain is involved in the association of the S-layer to the cell but is not essential in the interaction between individual PS2 proteins within the S-layer. A modified form of PS2, deleted of its C-terminal hydrophobic sequence, was constructed. The protein is almost unable to form an organized S-layer and is mainly released into the medium. We suggest that PS2 is anchored via its C-terminal hydrophobic sequence to a hydrophobic layer of the wall of the bacterium located some distance above the cytoplasmic membrane.
Abstract: The cell surface of Corynebacterium glutamicum grown on solid medium was totally covered with a highly ordered, hexagonal surface layer. Also, freeze-fracture revealed two fracture surfaces which were totally covered with ordered arrays displaying an hexagonal arrangement and the same unit cell dimension as the surface layer. The ordered arrays on the concave fracture surface, closest to the cell surface, were due to the presence of particles while those on the convex fracture surface were their imprints. The same cells grown on liquid medium displayed a cell surface and fracture surfaces only partially covered with ordered arrays. In this case, the ordered regions had the same relative position on the cell surface and on the fracture surfaces. All ordered arrays were totally absent in a mutant for cspB, the gene encoding PS2, one of the two major cell wall proteins. Treatment of the cells with proteinase K caused the gradual alteration of PS2 into a slightly lower molecular mass form. This was accompanied by a concomitant disappearance of the ordered fracture surfaces followed by the detachment of the ordered surface layer from the cell as large ordered patches displaying the same lattice symmetry and dimensions as those of the surface layer. The ordered patches were isolated. They contained the totality of PS2 initially associated with the cell. We conclude that the highly ordered surface layer of the intact cell was composed of PS2 interacting strongly with some cell wall material leading to its organization. This organized cell wall material produced fracture surfaces. We show that in the absence of intact PS2 protein on the cell wall, the same cell wall material was not organized and formed a structureless smooth layer.
Abstract: We show that inverted membrane vesicles from Corynebacterium glutamicum, a Gram-positive bacterium, are able to generate and maintain an electrochemical gradient of protons in response to the addition of NADH. This result indicates that the respiratory chain is intact and that the vesicles are reasonably impermeable to protons. These membrane vesicles may be the starting point for in vitro translocation studies of proteins in Gram-positive bacteria.
Abstract: PS1 is a protein translocated across the cytoplasmic membrane of Corynebacterium glutamicum, a Gram-positive bacterium. Western blots of whole cell extracts showed the presence of two bands associated with the mature and the precursor forms. Addition of chloramphenicol led to the disappearance of the precursor form while dissipation of the protonmotive force (delta microH) prior to the addition of chloramphenicol prevented the maturation of the precursor. Dissipation of delta microH prior to a pulse chase experiment resulted in a complete block on translocation; regeneration of delta microH allowed the translocation of PS1 synthesized in its absence. On the other hand, dissipation of delta microH immediately after a pulse period had little effect on PS1 secretion. Lowering the temperature to 10 degrees C at the end of the pulse period completely inhibited secretion. The efficiency of secretion as a function of increasing temperature followed closely the order-to-disorder transition of the membrane lipids as detected by fluorescence anisotropy of diphenylhexatriene. Taken together, the results show that delta microH and the state of the lipids affect different steps of PS1 secretion.
Abstract: PS2 is one of two major proteins detected in the culture media of various Corynebacterium glutamicum strains. The coding and promoter regions of the cspB gene encoding PS2 were cloned in lambda gt11 using polyclonal antibodies raised against PS2 for screening. Expression of the cspB gene in Escherichia coli led to the production of a major anti-PS2 labelled peptide of 63,000 Da, corresponding presumably to the mature form of PS2. It was detected in the cytoplasm, periplasm and surrounding medium of E. coli. Three other slower migrating bands of 65,000 68,000 and 72,000 Da were detected. The largest one probably corresponds to the precursor form of PS2 in E. coli. Analysis of the nucleotide sequence revealed an open reading frame (ORF) of 1533 nucleotides. The deduced 510-amino-acid polypeptide had a calculated molecular mass of 55,426 Da. According to the predicted amino acid sequence, PS2 is synthesized with a N-terminal segment of 30-amino-acid residues reminiscent of eukaryotic and prokaryotic signal peptides, and a hydrophobic domain of 21 residues near the C-terminus. Although no significant homologies were found with other proteins, it appears that some characteristics and the amino acid composition of PS2 share several common features with surface-layer proteins. The cspB gene was then disrupted in C. glutamicum by gene replacement. Freeze-etching electron microscopy performed on the wild-type strain indicated that the cell wall of C. glutamicum is covered with an ordered surface of proteins (surface layer, S-layer) which is in very close contact with other cell-wall components. These structures are absent from the cspB-disrupted strain but are present after reintroduction of the cspB gene on a plasmid into this mutant. Thus we demonstrate that the S-layer protein is the product of the cspB gene.
Abstract: Acyl Carrier Protein (ACP) is a small acidic protein which interacts with the various enzymes implicated in the biosynthesis of fatty acids in E. coli. It also interacts with the inner membrane proteins implicated in the biosynthesis of phospholipids. Samples of radioactive ACP were prepared with high specific activities and bearing photoactivable aryl azide derivatives. Two photoactivable reagents were used: para azido phenacyl bromide (pAPA) which reacts with the SH of the ACP prosthetic group and the N-hydroxysuccinimide ester of 4-azido salicylic acid (NHS-ASA) which reacts with the amino groups of the protein. Various methods were used to demonstrate that ACP could be cross-linked specifically to an inner membrane protein of E. coli, most probably to the glycerol-3-phosphate acyl transferase (GPAT). This covalent link should provide a powerful tool for further analysis of the structure of GPAT and its role in phospholipid biosynthesis. These photoactivable aryl azide derivatives of ACP could also be very useful for studying the interaction of ACP with the soluble enzymes implicated in fatty acid biosynthesis.
Abstract: Two proteins, PS1 and PS2, were detected in the culture medium of Corynebacterium glutamicum and are the major proteins secreted by this bacterium. No enzymatic activity was identified for either of the two proteins. Immunologically cross-reacting proteins were found in a variety of C. glutamicum strains but not in the coryneform Arthrobacter aureus. The gene encoding PS1, csp1, was cloned in lambda gt11 using polyclonal antibodies raised against PS1 to screen for producing clones. The csp1 gene was expressed in Escherichia coli, presumably from its own promoter, and directed the synthesis of two proteins recognized by anti-PS1 antibodies. The major protein band, of lower M(r), was detected in the periplasmic fraction. It had the same M(r) as the PS1 protein band detected in the supernatant of C. glutamicum cultures and presumably corresponds to the mature form of PS1. The minor protein band appears to be the precursor form of PS1. The nucleotide sequence of the csp1 gene was determined and contained an open reading frame encoding a polypeptide with a calculated molecular weight of 70,874, with a putative signal peptide with a molecular weight of 4411. This is consistent with the M(r) determined for PS1 from C. glutamicum culture supernatant and E. coli whole-cell extracts. The NH2-half of the deduced amino acid is similar (about 33% identical residues and 52% including similar residues) to the secreted antigen 85 protein complex of Mycobacterium. The csp1 gene in C. glutamicum was disrupted without any apparent effect on growth or viability.
Abstract: We report that membrane vesicles of Escherichia coli contain protein-binding sites for acyl carrier protein. Scatchard analysis of the binding indicates a dissociation constant around 0.35 micrometers and a maximum number of protein-binding sites around 50 pmol per mg of membrane protein. Binding is on the inner membrane while the outer membrane is devoid of binding sites. These results are consistent with the fact that some acyl carrier protein-dependent enzymes implicated in phospholipid- and membrane-derived oligosaccharide biosynthesis are localized in the cytoplasmic membrane.
Abstract: We [(1989) FEBS Lett., in press] have previously shown that membrane vesicles from Escherichia coli contain protein-binding sites for the acyl carrier protein (ACP). We report now that membrane vesicles prepared from a strain amplified for glycerol-3-phosphate acyltransferase (GPAT) contain a higher number of ACP-binding sites than the membrane vesicles prepared from a wild type strain. In addition, we show that GPAT is retained specifically on an ACP-Sepharose affinity column and that [3H]ACP binds to the enzyme solubilized by detergent. We conclude that GPAT, an inner membrane protein which catalyses the transesterification of a fatty acyl group from acyl coenzyme A or acyl ACP to glycerol-3-phosphate, possesses a binding site for ACP.
