ISSN:
1365-2958
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
,
Medicine
Notes:
The CorA Mg2+ transport system of Salmonella typhimurium mediates both influx and efflux of Mg2+. Mutations at the corA locus (83.5min) confer resistance to Co2+. Using transposon mutagenesis, three additional Co2+ resistance loci (corB, corC, and corD) were found and mapped to 55, 15, and 3min, respectively, on the S. typhimurium chromosome. No mutations corresponding to the reported corB locus at 95min in Escherichia coli were obtained. The corB, corC, and corD mutations confer levels of Co2+ resistance intermediate between those of the wild-type and corA mutations.Isogenic strains were constructed containing combinations of transposon insertion mutations in each of the three Co2+ resistance loci to assess their influence on the CorA Mg2+ transport system. The Vmax and Km values for 28Mg2+ or for 57Co2+ and 63Ni2+ influx, analogues of Mg2+ transported by the CorA system, were changed less than twofold compared with the wild-type values, regardless of the mutation(s) present. However, while efflux of 28Mg2+ through the CorA system was decreased threefold in strains carrying one or two mutant alleles among corB, corC, or corD, efflux was completely abolished in either a corA or a corBCD strain. Thus, although the corA gene product is necessary and sufficent to mediate Mg2+ influx, Mg2+ efflux requires the presence of a wild-type allele of at least one of the corB, corC or corD loci.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2958.1991.tb01984.x
