A bi-site mechanism for Escherichia coli F1-ATPase accounts for the observed positive catalytic cooperativity.

Nucleotide binding to nucleotide-depleted F(1)-ATPase from Escherichia coli (EcF(1)) during MgATP hydrolysis in the presence of excess epsilon subunit has been studied using a combination of centrifugal filtration and column-centrifugation methods. The results show that nucleotide-binding properties of catalytic sites on EcF(1) are affected by the state of occupancy of noncatalytic sites. The ATP-concentration dependence of catalytic-site occupancy during MgATP hydrolysis demonstrates that a bi-site mechanism is responsible for the positive catalytic cooperativity observed during multi-site catalysis by EcF(1). The results suggest that a bi-site mechanism is a general feature of F(1) catalysis.

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