TCB Publications - Abstract
Pius S. Padayatti, Josephine H. Leung, Paween Mahinthichaichan, Emad Tajkhorshid, Andrii Ishchenko, Vadim Cherezov, S. Michael Soltis, J. Baz Jackson, C. David Stout, Robert B. Gennis, and Qinghai Zhang. Critical role of water molecules in proton translocation by the membrane-bound transhydrogenase. Structure, 25:1111-1119, 2017. (PMC: PMC5524145)
in bacteria and eukaryotes. Here we
solved a 2.2-Åcrystal structure of the TH transmembrane domain
(Thermus thermophilus) at pH 6.5. This structure exhibits conformational
changes of helix positions from a previous structure solved at pH 8.5, and
reveals internal water molecules interacting with residues implicated in
proton translocation. Together with molecular dynamics simulations, we
show that transient water flows across a narrow pore and a hydrophobic
“dry” region in the middle of the membrane channel, with key residues
His42
(chain A) being protonated and Thr214
(chain B) displaying a conformational change, respectively, to gate the
channel access to both cytoplasmic and periplasmic chambers. Mutation of
Thr214 to Ala deactivated the enzyme. These data provide new
insights into the gating mechanism of proton translocation in TH.
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