The ATP synthase a-subunit of extreme alkaliphiles is a distinct variant: Mutations in the critical alkaliphile-specific residue Lys-180 and other residues that support alkaliphile oxidative phosphorylation

Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, New York, New York 10029, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 10/2010; 285(42):32105-15. DOI: 10.1074/jbc.M110.165084
Source: PubMed


A lysine residue in the putative proton uptake pathway of the ATP synthase a-subunit is found only in alkaliphilic Bacillus species and is proposed to play roles in proton capture, retention and passage to the synthase rotor. Here, Lys-180 was replaced
with alanine (Ala), glycine (Gly), cysteine (Cys), arginine (Arg), or histidine (His) in the chromosome of alkaliphilic Bacillus pseudofirmus OF4. All mutants exhibited octylglucoside-stimulated ATPase activity and β-subunit levels at least as high as wild-type.
Purified mutant F1F0-ATP synthases all contained substantial a-subunit levels. The mutants exhibited diverse patterns of native (no octylglucoside)
ATPase activity and a range of defects in malate growth and in vitro ATP synthesis at pH 10.5. ATP synthesis by the Ala, Gly, and His mutants was also impaired at pH 7.5 in the presence of a
protonophoric uncoupler. Thus Lys-180 plays a role when the protonmotive force is reduced at near neutral, not just at high
pH. The Arg mutant exhibited no ATP synthesis activity in the alkaliphile setting although activity was reported for a K180R
mutant of a thermoalkaliphile synthase (McMillan, D. G., Keis, S., Dimroth, P., and Cook, G. M. (2007) J. Biol. Chem. 282, 17395–17404). The hypothesis that a-subunits from extreme alkaliphiles and the thermoalkaliphile represent distinct
variants was supported by demonstration of the importance of additional alkaliphile-specific a-subunit residues, not found
in the thermoalkaliphile, for malate growth of B. pseudofirmus OF4. Finally, a mutant B. pseudofirmus OF4 synthase with switched positions of Lys-180 (helix 4) and Gly-212 (helix 5) retained significant coupled synthase activity
accompanied by proton leakiness.

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