Properties of recombinant cells capable of growing on serine without NhaB Na+/H+ antiporter in Escherichia coli.
Escherichia coli HIT-1 has a mutation in the Na+/H+ antiporter gene, nhaB (P. Thelen, T. Tsuchiya, and E. B. Goldberg, J. Bacteriol. 173:6553-6557, 1991). This strain is not able to utilize serine as a carbon source (T. Ishikawa, H. Hama, M. Tsuda, and T. Tsuchiya, J. Biol. Chem. 262:7443-7446, 1987), because an active NhaB is required to maintain the electrochemical potential of Na+, which drives serine transport via the Na+/serine carrier, the major transport system for serine. We isolated recombinant cells from a cross between strains HIT-1 and Hfr, and these cells were able to grow on serine even though the NhaB Na+/H+ antiporter of the recombinant cells was still defective. We found that the activity of the H+/serine cotransport system, one of the minor serine transport systems in E. coli, was elevated in the recombinant cells. H+/serine cotransport activity was induced by leucine in the recombinant cells more strongly than in strain HIT-1. A kinetic analysis showed that the Vmax, but not the Km, of the transport system was much higher in the recombinant cells than in strain HIT-1 cells.
Kayahara
T
T
Department of Microbiology, Faculty of Pharmaceutical Sciences, Okayama University, Japan.
Thelen
P
P
Ogawa
W
W
Inaba
K
K
Tsuda
M
M
Goldberg
E B
EB
Tsuchiya
T
T
D001692:Biological Transport / Q000235:genetics; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D005798:Genes, Bacterial; D005990:Glycerol / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009154:Mutation; D011995:Recombination, Genetic; D012694:Serine / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers
D002352:Carrier Proteins; D017923:Sodium-Hydrogen Exchangers; D012694:Serine; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D005990:Glycerol