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Figure 4.
Figure 4: Structural basis of Na^+/H+ translocation and pH
regulation. a, Stereo view of TMSs oriented parallel to the
membrane, with the cytoplasmic side at the top. The colour code
is as in Fig. 2. Residues whose alterations affect pH
regulation12,16,31, apparent K[m] (refs 29, 38) or both29,38 are
shown with side chains and labelled blue, black and purple,
respectively. The putative 'pH sensor' is encircled. The
approximate position of the cytoplasmic passage is marked by red
dotted lines connecting Asp 164 with residues lining the funnel
entry. b, Close interactions between helix IX and helices IVc
and XIp that are important for pH regulation. Van der Waals
contacts between side chains are indicated with dotted red lines.
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