An Escherichia coli gene (FabZ) encoding (3R)-hydroxymyristoyl acyl carrier protein dehydrase. Relation to fabA and suppression of mutations in lipid A biosynthesis.
Escherichia coli strain SM101 harbors a temperature-sensitive allele (lpxA2) of the gene encoding UDP-Glc-NAc acyltransferase (the first enzyme of the lipid A pathway). SM101 is temperature-sensitive for lipid A biosynthesis and growth. To determine whether or not E. coli mutants lacking lipid A can be isolated, we examined temperature-resistant revertants of SM101. All regained the ability to synthesize lipid A. However, some were not true revertants but had acquired mutations in a neighboring gene (orf17), while retaining the original lpxA2 lesion. Cell extracts of such revertants displayed 2-5 fold reductions in the specific activity of (3R)-hydroxymyristoyl-ACP dehydrase. Wild-type cells that overproduced the protein encoded by orf17 overproduced (3R)-hydroxymyristoyl-ACP dehydrase activity as much as 170-fold, suggesting that orf17 is the structural gene for the dehydrase. The proposed function of orf17 is further supported by its sequence similarity to fabA, the structural gene for (3R)-hydroxydecanoyl dehydrase of E. coli. We suggest that bypass of the lpxA2 phenotype by mutations in orf17 may be due to an increased (3R)-hydroxymyristoyl-ACP pool. The orf17 gene (which we now designate fabZ) is not regulated by fadR. However, orf17 may be related to sefA, a suppressor of certain lesions in the cell division/lipid A biosynthesis gene, envA.
Mohan
S
S
Department of Biochemistry, Merck Research Laboratories, Rahway, New Jersey 07065.
Kelly
T M
TM
Eveland
S S
SS
Raetz
C R
CR
Anderson
M S
MS
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D054889:Fatty Acid Synthase, Type II; D036781:Fimbriae Proteins; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D005798:Genes, Bacterial; D006358:Hot Temperature; D006836:Hydro-Lyases / Q000235:genetics*; D008050:Lipid A / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D009154:Mutation; D009237:N-Acetyllactosamine Synthase / Q000235:genetics / Q000378:metabolism; D009838:Oligodeoxyribonucleotides; D012097:Repressor Proteins / Q000235:genetics; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; C057119:FadR protein, Bacteria; D008050:Lipid A; D009838:Oligodeoxyribonucleotides; D012097:Repressor Proteins; C080931:sefA protein, Salmonella enteritidis; D036781:Fimbriae Proteins; D009237:N-Acetyllactosamine Synthase; D006836:Hydro-Lyases; C047118:3-hydroxyacyl-(acyl-carrier-protein) dehydratase; D054889:Fatty Acid Synthase, Type II