Hybrid ATPase's Formed from Subunits of Coupling Factor Fi's of Escherichia coli and Thermophilic Bacterium PS31

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Abstract
ATPase complexes were reconstituted from homologous and heterologous combinations of α β, and γsubunits of coupling factor ATPase TF 1 of thermophilic bacterium PS3 and EF 1 of Escherichia coli . TF 1 and theαβγ complex reconstituted from TF 1 subunits were thermostable and activated by methanol, sodium dodecyl sulfate and anions and they were halophilic, whereas EF 1 and its three-subunit complex did not show these properties. The hybrid ATPase α T β T γ E (complex of the α and β subunits of TF 1 and the γ subunit of EF 1 showed closely similar properties to TF 1 except for thermostability, while α E β E γ T (a and β from EF 1 andγ from TF 1 ) had similar properties to EF 1 . These results suggest that α and/or β is required for the properties of F 1 The complex α E β T γ E showed similar properties to EF 1 except for its optimum pH: this complex had a broad pH optimum at about pH 7, whereas EF 1 had an optimum at pH 8.5. No hybrid complexes were thermostable, suggesting that all three subunits of TF 1 are required for heat stability. These hybrids showed higher halophilicity than EF 1 ; although they were less halophilic than TF 1 The hybrid enzymes studied here are the first thermophilic-mesophilic hybrid enzymes obtained.

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