Significance of the glutamate-139 residue of the V-type Na+-ATPase NtpK subunit in catalytic turnover linked with salt tolerance of Enterococcus hirae |
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| Authors: | Kawano-Kawada Miyuki Takahashi Hiroko Igarashi Kazuei Murata Takeshi Yamato Ichiro Homma Michio Kakinuma Yoshimi |
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| Affiliation: | Integrated Center for Sciences, Ehime University, Matsuyama, Japan1; Graduate School of Pharmaceutical Sciences, Chiba University, Chiba, Japan. |
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| Abstract: | A Glu139Asp mutant of the NtpK subunit (kE139D) of Enterococcus hirae vacuolar-type ATPase (V-ATPase) lost tolerance to sodium but not to lithium at pH 10. Purified kE139D V-ATPase retained relatively high specific activity and affinity for the lithium ion compared to the sodium ion. The kE139 residue of V-ATPase is indispensable for its enzymatic activity that is linked with the salt tolerance of enterococci. |
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