title: Properties of F1-ATPase from the uncD412 mutant of Escherichia coli.
abstract: Properties of purified F1-ATPase from Escherichia coli mutant strain AN484 (uncD412) have been studied in an attempt to understand why the amino acid substitution in the beta-subunit of this enzyme causes a tenfold reduction from normal MgATP hydrolysis rate. In most properties that were studied, uncD412 F1-ATPase resembled normal E. coli F1-ATPase. Both enzymes were found to contain a total of six adenine-nucleotide-binding sites, of which three were found to be non-exchangeable and three were exchangeable (catalytic) sites. Binding of the non-hydrolysable substrate analogue adenosine 5'-[beta gamma-imido]triphosphate (p[NH]ppA) to the three exchangeable sites showed apparent negative co-operativity. The binding affinities for p[NH]ppA, and also ADP, at the exchangeable sites were similar in the two enzymes. Both enzymes were inhibited by efrapeptin, aurovertin and p[NH]ppA, and were inactivated by dicyclohexylcarbodi-imide, 4-chloro-7-nitrobenzofurazan and p-fluorosulphonyl-benzoyl-5'-adenosine. Km values for CaATP and MgATP were similar in the two enzymes. uncD412 F1-ATPase was abnormally unstable at high pH, and dissociated into subunits readily with consequent loss of activity. The reason for the impairment of catalysis in uncD412 F1-ATPase cannot be stated with certainty from these studies. However we discuss the possibility that the mutation interrupts subunit interaction, thereby causing a partial impairment in the site-site co-operativity which is required for 'promotion' of catalysis in this enzyme.
mesh_terms: D009327:4-Chloro-7-nitrobenzofurazan / Q000494:pharmacology; D000227:Adenine Nucleotides / Q000378:metabolism; D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000266:Adenylyl Imidodiphosphate / Q000378:metabolism; D001313:Aurovertins / Q000494:pharmacology; D001665:Binding Sites; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D004926:Escherichia coli / Q000201:enzymology*; D007700:Kinetics; D009154:Mutation; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D000227:Adenine Nucleotides; D001313:Aurovertins; D000266:Adenylyl Imidodiphosphate; D004024:Dicyclohexylcarbodiimide; C039026:aurovertin D; C010959:5'-(4-fluorosulfonylbenzoyl)adenosine; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases; D009327:4-Chloro-7-nitrobenzofurazan; D000241:Adenosine