Identification of a pH regulated Na(+)/H(+) antiporter of Methanococcus jannaschii |
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Authors: | Hellmer Jens Pätzold Ralf Zeilinger Carsten |
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Institution: | Universit?t Hannover, Institut für Biophysik, Herrenh?userstr. 2, D-30419, Hannover, Germany. |
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Abstract: | The genome of the hyperthermophilic archaeon Methanococcus jannaschii contains three Na(+)/H(+) antiporter related genes Mj0057, Mj1521 and Mj1275. Comparative sequence alignments revealed that Mj0057 and Mj1521 belong to the NhaP family whereas Mj1275 is a member of the NapA family. The genes were cloned and expressed in the double mutant Escherichia coli strain Frag144 (DeltanhaA, DeltanhaB) to analyze their capability of mediating DeltapH driven Na(+) flux in everted vesicles. From the tested clones only Mj0057 displayed Na(+) (Li(+))/H(+) antiporter activity. The transport was pH dependent and occurred at pH 7.0 and below. At pH 6.0 the apparent K(m) values for Na(+) and Li(+) were approximately 10 and 2.5 mM, respectively. |
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