NhaK, a novel monovalent cation/H+ antiporter of Bacillus subtilis.
Four Na+/H+ antiporters, Mrp, TetA(L), NhaC, and MleN have so far been described in Bacillus subtilis 168. We identified an additional Na+/H+ antiporter, YvgP, from B. subtilis that exhibits homology to the cation: proton antiporter-1 (CPA-1) family. The yvgP-dependent complementation observed in a Na+(Ca2+)/H+ antiporter-defective Escherichia coli mutant (KNabc) suggested that YvgP effluxed Na+ and Li+. In addition, effects of yvgP expression on a K+ uptake-defective mutant of E. coli indicated that YvgP also supported K+ efflux. In a fluorescence-based assay of everted membrane vesicles prepared from E. coli KNabc transformants, YvgP-dependent Na+ (K+, Li+, Rb+)/H+ antiport activity was demonstrated. Na+ (K+, Li+)/H+ activity was higher at pH 8.5 than at pH 7.5. Mg2+, Ca2+ and Mn2+ did not serve as substrates but they inhibited YvgP antiport activities. Studies of yvgP expression in B. subtilis, using a reporter gene fusion, showed a significant constitutive level of expression that was highest in stationary phase, increasing as stationary phase progressed. In addition, the expression level was significantly increased in the presence of added K+ and Na+.
Fujisawa
Makoto
M
Graduate School of Life Sciences, Toyo University, 1-1-1 Izumino, Itakura-machi, Oura-gun, Gunma, 374-0193, Japan.
Kusumoto
Ayumi
A
Wada
Yuko
Y
Tsuchiya
Takahiro
T
Ito
Masahiro
M
D017920:Antiporters / Q000235:genetics / Q000378:metabolism*; D001412:Bacillus subtilis / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002412:Cations; D004926:Escherichia coli / Q000378:metabolism; D017353:Gene Deletion; D006859:Hydrogen; D006863:Hydrogen-Ion Concentration; D008094:Lithium / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D011188:Potassium / Q000378:metabolism; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D013379:Substrate Specificity; D001616:beta-Galactosidase / Q000378:metabolism
D017920:Antiporters; D001426:Bacterial Proteins; D002412:Cations; D006859:Hydrogen; D008094:Lithium; D012964:Sodium; D001616:beta-Galactosidase; D012413:Rubidium; D011188:Potassium