Mutants of Escherichia coli K-12 that are resistant to a selenium analog of lipoic acid identify unknown genes in lipoate metabolism

Kelynne E. Reed, Timothy W. Morris, John E. Cronan

Research output: Contribution to journalArticlepeer-review

Abstract

Lipoic acid is a disulfide-containing cofactor required for the reactions catalyzed by α-ketoacid dehydrogenase enzyme complexes. We report the chemical synthesis and biological properties of lipoic acid analogs in which one or both sulfur atoms were replaced by selenium. Replacement of either the C-6 or the C-8 sulfur atom with selenium results in lipoic acid derivatives with apparently unaltered biological properties. However, simultaneous replacement of both sulfur atoms gave an analog (selenolipoic acid) that inhibited growth of wild-type Escherichia coli when present in minimal glucose medium at 50 ng/ml. This growth inhibition was reversed by the addition of either excess lipoic acid or acetate plus succinate. Labeling experiments with [75Se]selenolipoic acid showed that this compound was efficiently incorporated into the α-ketoacid dehydrogenase complexes of growing cells. Spontaneously arising selenolipoic acid-resistant (slr) mutants were isolated. Two of these isolates resistant to high levels of selenolipoic acid were studied in detail. The slr-1 mutation, which was mapped to min 99.6 of the E. coli chromosome, increased the lipoate requirement of lipA strains by 4-fold and appeared to define a gene encoding a lipoate-protein ligase. The slr-7 mutation, which was mapped to min 15.25 of the chromosome, completely suppressed the lipoate requirement of lipA strains and defined a gene of unknown function in the synthesis of lipoic acid.

Original languageEnglish (US)
Pages (from-to)3720-3724
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume91
Issue number9
DOIs
StatePublished - Apr 26 1994

ASJC Scopus subject areas

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