The properties of hybrid F1-ATPase enzymes suggest that a cyclical catalytic mechanism involving three catalytic sites occurs

R. Rao, A. E. Senior

Research output: Contribution to journalArticle

Abstract

Maximal rates of ATP hydrolysis catalyzed by F1-ATPase enzymes are known to involve strong positive catalytic site cooperativity. There are three potential catalytic nucleotide-binding sites on F1. Two important and unanswered questions are (i) whether all three potential catalytic sites must interact cooperatively to yield maximal rates of ATP hydrolysis and (ii) whether a cyclical three-site mechanism operates as suggested by several authors. We have studied these two questions here by measuring the ATPase activities of hybrid enzymes containing normal β-, γ-, δ-, and ε-subunits together with different combinations of mutant and normal α-subunits. The mutant α-subunits were derived from uncA401, uncA447, and uncA453 mutant E. coli F1-ATPase, in which positive cooperativity between catalytic sites is strongly attenuated by defined mis-sense mutations. Our data show that three normal catalytic sites are required to interact in order to achieve maximal ATPase rates and suggest that a cyclical mechanism does operate. Hybrid enzyme containing one-third mutant α-subunit and two-thirds normal α-subunits had substantial but submaximal activity, showing that cooperativity between three sites in a noncyclical fashion, or between pairs of sites, can achieve effective catalysis.

Original languageEnglish (US)
Pages (from-to)17450-17454
Number of pages5
JournalJournal of Biological Chemistry
Volume262
Issue number36
StatePublished - Jan 1 1987
Externally publishedYes

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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