Characterization of Escherichia coli men mutants defective in conversion of o-succinylbenzoate to 1,4-dihydroxy-2-naphthoate.

Four independent menaquinone (vitamin K-deficient mutants of , blocked in the conversion of o-succinylbenzoate (OSB) to 1,4-dihydroxy-2-naphthoate (DHNA), were found to represent two distinct classes. Enzymatic complementation was observed when a cell-free extract of one mutant was mixed with extracts of any of the remaining three mutants. The missing enzymes in the two classes were identified by in vitro complementation with preparations of OSB-coenzyme A (CoA) synthetase or DHNA synthase isolated from . Mutants lacking DHNA synthase (and therefore complementing with DHNA synthase) were designated , and the mutant lacking OSB-CoA synthetase (and therefore complementing with OSB-CoA synthetase) was designated . The mutants produced only the spirodilactone form of OSB when extracts were incubated with [2,3-C]OSB, ATP, and CoA; the OSB was unchanged on incubation with an extract from the mutant under these conditions. Experiments with strains lysogenized by a transducing phage (λG68) and transduction studies with phage P1 indicated that the and genes form part of a cluster of four genes, controlling the early steps in menaquinone biosynthesis, located at 48.5 min in the linkage map. Evidence was obtained for the clockwise gene order , where the asterisk denotes the uncertain position of relative to and . The transducing phage (λG68) contained functional , , and genes, but only part of the gene, and it was designated λ .