Genetic analysis of the γ aminobutyrate utilization pathway in Escherichia coli K 12

Abstract

The control mutation that results in a concomitant severalfold increase in the activites of γ aminobutyrate α ketoglutarate transaminase (GSST, EC 2.6.1.19) and succinic semialdehyde dehydrogenase (SSDH, EC 1.2.1.16), leading to the acquisition of the ability to utilize γ aminobutyrate (GABA) as the sole source of nitrogen by Escherichia coli K 12 mutants, was mapped by mating and transduction with P1kc. The locus affected, gabC, is approx. 48% co transduced with the thyA gene, located at min 55 of the E. coli K 12 chromosome. The structural gene of the first enzyme in the GABA pathway, GSST, was mapped by interrupted mating, using one of the GSST less mutants, DB742, isolated in this work. The mutated locus, gabT, is situated at about min 73 of the E. coli chromosome, close to the gltC gene.