An Escherichia coli gene (FabZ) encoding (3R)-hydroxymyristoyl acyl carrier protein dehydrase. Relation to fabA and suppression of mutations in lipid A biosynthesis

• Published in: The Journal of biological chemistry 1994-12, Vol.269 (52), p.32896-32903
• Main Authors: Mohan, S, Kelly, T M, Eveland, S S, Raetz, C R, Anderson, M S
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Bacterial Proteins - genetics; Base Sequence; Escherichia coli; Escherichia coli - enzymology; Escherichia coli - genetics; Fatty Acid Synthase, Type II; Fimbriae Proteins; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Enzymologic; Genes, Bacterial; Hot Temperature; Hydro-Lyases - genetics; Lipid A - biosynthesis; Molecular Sequence Data; Mutation; N-Acetyllactosamine Synthase - genetics; N-Acetyllactosamine Synthase - metabolism; Oligodeoxyribonucleotides; Repressor Proteins - genetics; Sequence Homology, Amino Acid
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/s0021-9258(20)30075-2

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.