Unisite catalysis and the delta subunit of F1-ATPase in Escherichia coli.
The 5-subunit form of the Escherichia coli F1-ATPase, characterized by the subunit composition alpha 3 beta 3 gamma delta epsilon, failed to exhibit a rate acceleration when samples of the enzyme hydrolyzing substoichiometric concentrations of [gamma-32P]ATP were switched from unisite to multisite hydrolysis by the addition of a cold chase. A 4-subunit form of the enzyme lacking in the delta subunit (alpha 3 beta 3 gamma epsilon) did exhibit cold chase-promoted accelerations in the hydrolysis of ATP. Reconstitution of a 5-subunit enzyme by incubating the 4-subunit form of the enzyme with a purified preparation of subunit delta was accompanied by a disappearance in the response to a cold chase. The rate constants and equilibrium constants for unisite catalysis by the 4-subunit enzyme did not differ significantly from previously reported values that may have been based on a mixture of 4- and 5-subunit forms of the enzyme. The vesicular form of Escherichia coli F0F1-ATPase exhibited a response to a cold chase only if the vesicles were first extracted with KCl. [gamma-32P]ATP bound in the high affinity catalytic sites of KCl-extracted membranes partially dissociated in an energy-dependent manner when the vesicles oxidized NADH.
Xiao
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Department of Biochemistry and Molecular Biology, State University of New York, Syracuse 13210.
Penefsky
H S
HS
D000255:Adenosine Triphosphate / Q000378:metabolism*; D002384:Catalysis; D004926:Escherichia coli / Q000201:enzymology*; D006868:Hydrolysis; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D011487:Protein Conformation; D006180:Proton-Translocating ATPases / Q000302:isolation & purification / Q000378:metabolism*; D013329:Structure-Activity Relationship
D011189:Potassium Chloride; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases