| Budget Amount *help |
¥4,030,000 (Direct Cost: ¥3,100,000、Indirect Cost: ¥930,000)
Fiscal Year 2016: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2015: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2014: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
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| Outline of Final Research Achievements |
Vacuolar-type ATPases (V-ATPases) structurally resemble F-ATPases and function as proton pump in acidic organelles and plasma membranes of eukaryotic cells as well as in bacteria. The Enterococcus hirae V-ATPase is a unique variant of V-ATPase, which recognizes sodium and lithium with near equal affinity and is indispensable for salt tolerance of this bacterium at alkaline pH. We previously indicated that NtpK(E139D) mutant strain lost tolerance to sodium but not to lithium, and suggested that the E139 residue is indispensable for the enzymatic activity of E. hirae V-ATPase. In an attempt to isolate the suppressor mutations for NtpK(E139D), we isolated two mutants, NtpK(E50K/E139D) and NtpK(V138I/E139D). Interestingly, the single point mutation of NtpK(E50K) or NtpK(E50D) decreased the activities of V-ATPase to approximately 50% of the wild-type, suggesting that E50 is one of the important residues for the enzymatic activity of E. hirae V-ATPase.
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