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pH‐induced structural change in a sodium/proton antiporter from Methanococcus jannaschii
Author(s) -
Vinothkumar Kutti R,
Smits Sander HJ,
Kühlbrandt Werner
Publication year - 2005
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/sj.emboj.7600727
Subject(s) - methanococcus , biology , antiporter , sodium , proton , biochemistry , methanosarcina barkeri , biophysics , genetics , bacteria , archaea , membrane , materials science , methanogenesis , physics , gene , quantum mechanics , metallurgy
Na + /H + antiporters are pH‐dependent membrane transport proteins that maintain the homeostasis of H + and Na + in living cells. MjNhaP1 from Methanococcus jannaschii , a hyperthermophilic archaeon that grows optimally at 85°C, was cloned and expressed in Escherichia coli . Two‐dimensional crystals were obtained from purified protein at pH 4. Electron cryomicroscopy yielded an 8 Å projection map. Like the related E. coli antiporter NhaA, MjNhaP1 is a dimer, but otherwise the structures of the two antiporters differ significantly. The map of MjNhaP1 shows elongated densities in the centre of the dimer and a cluster of density peaks on either side of the dimer core, indicative of a bundle of 4–6 membrane‐spanning helices. The effect of pH on the structure of MjNhaP1 was studied in situ . A major change in density distribution within the helix bundle, and a ∼2 Å shift in the position of the helix bundle relative to the dimer core occurred at pH 6 and above. The two conformations at low and high pH most likely represent the closed and open states of the antiporter.