A mutant of Escherichia coli conditionally defective in the synthesis of holo-[acyl carrier protein].

Supplementation of Escherichia coli pantothenate auxotrophs with varying concentrations of pantothenate results in a concomitant variation of the intracellular level of CoA but has no effect on the level of holo-[acyl carrier protein] (holo-[ACP]) (Alberts, A., and Vagelos, P. R. (1966) J. Biol. Chem. 241, 5201-5204). The 4-phosphopantetheine moiety of CoA is transferred by the enzyme holo-[ACP] synthase to apo-[acyl carrier protein] (apo-[ACP]) to form holo-[ACP], the form active in lipid synthesis. We mutagenized an E. coli K12 pantothenate auxotroph and selected for mutants unable to grow on a low concentration of pantothenate (0.25 microM) but that grew on a much higher level (25 microM). One of these strains was completely deficient in holo-[ACP] synthase. Reversion and recombinational genetic analyses indicated that the mutant growth phenotype was due to an altered holo-[ACP] synthase activity. The changes in the intracellular levels of CoA and holo-[ACP] engendered by manipulation of the levels of pantothenate supplementation were consistent with a deficiency in holo-[ACP] synthase activity in cultures supplemented with low levels of pantothenate. The site of the genetic lesion (called acpS) was localized on the E. coli genetic map.