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Publication Abstract from PubMed

Membrane-embedded pyrophosphatase (M-PPase) hydrolyzes pyrophosphate to drive ion (H(+) and/or Na(+)) translocation. We determined crystal structures and functions of Vigna radiata M-PPase (VrH(+)-PPase), the VrH(+)-PPase-2Pi complex and mutants at hydrophobic gate (residue L555) and exit channel (residues T228 and E225). Ion pore diameters along the translocation pathway of three VrH(+)-PPases complexes (Pi-, 2Pi- and imidodiphosphate-bound states) present a unique wave-like profile, with different pore diameters at the hydrophobic gate and exit channel, indicating that the ligands induced pore size alterations. The 2Pi-bound state with the largest pore diameter might mimic the hydrophobic gate open. In mutant structures, ordered waters detected at the hydrophobic gate among VrH(+)-PPase imply the possibility of solvation, and numerous waters at the exit channel might signify an open channel. A salt-bridge, E225-R562 is at the way out of the exit channel of VrH(+)-PPase; E225A mutant makes the interaction eliminated and reveals a decreased pumping ability. E225-R562 might act as a latch to regulate proton release. A water wire from the ion gate (R-D-K-E) through the hydrophobic gate and into the exit channel may reflect the path of proton transfer.

Roles of the Hydrophobic Gate and Exit Channel in Vigna radiata Pyrophosphatase Ion Translocation.,Tsai JY, Tang KZ, Li KM, Hsu BL, Chiang YW, Goldman A, Sun YJ J Mol Biol. 2019 Apr 5;431(8):1619-1632. doi: 10.1016/j.jmb.2019.03.009. Epub, 2019 Mar 13. PMID:30878480^[5]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.