Membrane pyrophosphatases from Thermotoga maritima and Vigna radiata suggest a conserved coupling mechanism

Kun-Mou Li, Craig Wilkinson, Juho Kellosalo, Jia-Yin Tsai, Tommi Kajander, Lars J. C. Jeuken, Yuh-Ju Sun () and Adrian Goldman ()
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Kun-Mou Li: College of Life Science, National Tsing Hua University
Craig Wilkinson: Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds
Juho Kellosalo: University of Helsinki, Helsinki
Jia-Yin Tsai: College of Life Science, National Tsing Hua University
Tommi Kajander: Institute of Biotechnology, University of Helsinki
Lars J. C. Jeuken: Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds
Yuh-Ju Sun: College of Life Science, National Tsing Hua University
Adrian Goldman: Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds

Nature Communications, 2016, vol. 7, issue 1, 1-11

Abstract: Abstract Membrane-bound pyrophosphatases (M-PPases), which couple proton/sodium ion transport to pyrophosphate synthesis/hydrolysis, are important in abiotic stress resistance and in the infectivity of protozoan parasites. Here, three M-PPase structures in different catalytic states show that closure of the substrate-binding pocket by helices 5–6 affects helix 13 in the dimer interface and causes helix 12 to move down. This springs a ‘molecular mousetrap’, repositioning a conserved aspartate and activating the nucleophilic water. Corkscrew motion at helices 6 and 16 rearranges the key ionic gate residues and leads to ion pumping. The pumped ion is above the ion gate in one of the ion-bound structures, but below it in the other. Electrometric measurements show a single-turnover event with a non-hydrolysable inhibitor, supporting our model that ion pumping precedes hydrolysis. We propose a complete catalytic cycle for both proton and sodium-pumping M-PPases, and one that also explains the basis for ion specificity.

Date: 2016
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DOI: 10.1038/ncomms13596

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