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J Biol Chem. 2015 Jan 9;290(2):1197-209. doi: 10.1074/jbc.M114.568139. Epub 2014 Dec 1.

Substrate-induced changes in domain interaction of vacuolar H⁺-pyrophosphatase.

Author information

1
From the Department of Nephrology, Kidney Research Center, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan 33333.
2
the Department of Life Science and Institute of Bioinformatics and Structural Biology, College of Life Science, and.
3
Department of Engineering and System Science, College of Nuclear Science, National Tsing Hua University, Hsin Chu 30013, Taiwan.
4
From the Department of Nephrology, Kidney Research Center, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan 33333, cwyang@ms1.hinet.net.
5
the Department of Life Science and Institute of Bioinformatics and Structural Biology, College of Life Science, and rlpan@life.nthu.edu.tw.

Abstract

Single molecule atomic force microscopy (smAFM) was employed to unfold transmembrane domain interactions of a unique vacuolar H(+)-pyrophosphatase (EC 3.6.1.1) from Vigna radiata. H(+)-Pyrophosphatase is a membrane-embedded homodimeric protein containing a single type of polypeptide and links PPi hydrolysis to proton translocation. Each subunit consists of 16 transmembrane domains with both ends facing the lumen side. In this investigation, H(+)-pyrophosphatase was reconstituted into the lipid bilayer in the same orientation for efficient fishing out of the membrane by smAFM. The reconstituted H(+)-pyrophosphatase in the lipid bilayer showed an authentically dimeric structure, and the size of each monomer was ∼4 nm in length, ∼2 nm in width, and ∼1 nm in protrusion height. Upon extracting the H(+)-pyrophosphatase out of the membrane, force-distance curves containing 10 peaks were obtained and assigned to distinct domains. In the presence of pyrophosphate, phosphate, and imidodiphosphate, the numbers of interaction curves were altered to 7, 8, and 10, respectively, concomitantly with significant modification in force strength. The substrate-binding residues were further replaced to verify these domain changes upon substrate binding. A working model is accordingly proposed to show the interactions between transmembrane domains of H(+)-pyrophosphatase in the presence and absence of substrate and its analog.

KEYWORDS:

Atomic Force Microscopy (AFM); Bioenergetics; Force-Distance Curve; Membrane Transporter Reconstitution; Protein-Protein Interaction; Proton Pump; Vacuolar H+-pyrophosphatase

PMID:
25451931
PMCID:
PMC4294485
DOI:
10.1074/jbc.M114.568139
[Indexed for MEDLINE]
Free PMC Article

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