Significance of the glutamate-139 residue of the V-type Na+-ATPase NtpK subunit in catalytic turnover linked with salt tolerance of Enterococcus hirae.
نویسندگان
چکیده
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.
منابع مشابه
Structure of the rotor of the V-Type Na+-ATPase from Enterococcus hirae.
The membrane rotor ring from the vacuolar-type (V-type) sodium ion-pumping adenosine triphosphatase (Na+-ATPase) from Enterococcus hirae consists of 10 NtpK subunits, which are homologs of the 16-kilodalton and 8-kilodalton proteolipids found in other V-ATPases and in F1Fo- or F-ATPases, respectively. Each NtpK subunit has four transmembrane alpha helices, with a sodium ion bound between helice...
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The crystal structures of the Na(+)- and Li(+)-bound NtpK rings of Enterococcus hirae V-ATPase have been obtained. The coupling ion (Na(+) or Li(+)) was surrounded by five oxygen atoms contributed by residues T64, Q65, Q110, E139, and L61, and the hydrogen bonds of the side chains of Q110, Y68, and T64 stabilized the position of the E139 γ carboxylate essential for ion occlusion (PDB accession ...
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عنوان ژورنال:
- Journal of bacteriology
دوره 193 14 شماره
صفحات -
تاریخ انتشار 2011