The role of the βDELSEED-loop of ATP synthase

Nelli Mnatsakanyan, Arathianand M. Krishnakumar, Toshiharu Suzuki, Joachim Weber

Research output: Contribution to journalArticle

27 Scopus citations

Abstract

ATP synthase uses a unique rotational mechanism to convert chemical energy into mechanical energy and back into chemical energy. The helix-turn-helix motif, termed "DELSEED-loop," in the C-terminal domain of the β subunit was suggested to be involved in coupling between catalysis and rotation. Here, the role of the DELSEED-loop was investigated by functional analysis of mutants of Bacillus PS3 ATP synthase that had 3-7 amino acids within the loop deleted. All mutants were able to catalyze ATP hydrolysis, some at rates several times higher than the wild-type enzyme. In most cases ATP hydrolysis in membrane vesicles generated a transmembrane proton gradient, indicating that hydrolysis occurred via the normal rotational mechanism. Except for two mutants that showed low activity and low abundance in the membrane preparations, the deletion mutants were able to catalyze ATP synthesis. In general, the mutants seemed less well coupled than the wild-type enzyme, to a varying degree. Arrhenius analysis demonstrated that in the mutants fewer bonds had to be rearranged during the rate-limiting catalytic step; the extent of this effect was dependent on the size of the deletion. The results support the idea of a significant involvement of the DELSEED-loop in mechanochemical coupling in ATP synthase. In addition, for two deletion mutants it was possible to prepare an α3β 3γ subcomplex and measure nucleotide binding to the catalytic sites. Interestingly, both mutants showed a severely reduced affinity for MgATP at the high affinity site.

Original languageEnglish
Pages (from-to)11336-11345
Number of pages10
JournalJournal of Biological Chemistry
Volume284
Issue number17
DOIs
StatePublished - Apr 24 2009

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