title: Functional replacement of the FabA and FabB proteins of Escherichia coli fatty acid synthesis by Enterococcus faecalis FabZ and FabF homologues.
abstract: The anaerobic unsaturated fatty acid synthetic pathway of Escherichia coli requires two specialized proteins, FabA and FabB. However, the fabA and fabB genes are found only in the Gram-negative alpha- and gamma-proteobacteria, and thus other anaerobic bacteria must synthesize these acids using different enzymes. We report that the Gram-positive bacterium Enterococcus faecalis encodes a protein, annotated as FabZ1, that functionally replaces the E. coli FabA protein, although the sequence of this protein aligns much more closely with E. coli FabZ, a protein that plays no specific role in unsaturated fatty acid synthesis. Therefore E. faecalis FabZ1 is a bifunctional dehydratase/isomerase, an enzyme activity heretofore confined to a group of Gram-negative bacteria. The FabZ2 protein is unable to replace the function of E. coli FabZ, although FabZ2, a second E. faecalis FabZ homologue, has this ability. Moreover, an E. faecalis FabF homologue (FabF1) was found to replace the function of E. coli FabB, whereas a second FabF homologue was inactive. From these data it is clear that bacterial fatty acid biosynthetic pathways cannot be deduced solely by sequence comparisons.
authors.affiliation: Department of Microbiology, University of Illinois, 601 S. Goodwin Avenue, Urbana, IL 61801, USA.
authors.forename: Haihong
authors.initials: H
authors.lastname: Wang
authors.forename: John E
authors.initials: JE
authors.lastname: Cronan
mesh_terms: D015099:3-Oxoacyl-(Acyl-Carrier-Protein) Synthase / Q000235:genetics / Q000502:physiology*; D000213:Acyl Carrier Protein / Q000737:chemistry; D001089:Arabinose / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology*; D002474:Cell-Free System; D004247:DNA / Q000378:metabolism; D013293:Enterococcus faecalis / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D054889:Fatty Acid Synthase, Type II; D005227:Fatty Acids / Q000096:biosynthesis* / Q000737:chemistry*; D005816:Genetic Complementation Test; D006836:Hydro-Lyases / Q000235:genetics / Q000502:physiology*; D009097:Multienzyme Complexes / Q000235:genetics*; D009154:Mutation; D010743:Phospholipids / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism
chemical_list: D000213:Acyl Carrier Protein; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C490371:FabZ protein, Enterococcus faecalis; D005227:Fatty Acids; D009097:Multienzyme Complexes; D010743:Phospholipids; D004247:DNA; D001089:Arabinose; D015099:3-Oxoacyl-(Acyl-Carrier-Protein) Synthase; C490369:FabB protein, E coli; C490370:FabF protein, Enterococcus faecalis; D006836:Hydro-Lyases; C047118:3-hydroxyacyl-(acyl-carrier-protein) dehydratase; D054889:Fatty Acid Synthase, Type II