title: Guanosine and formycin triphosphates bind at non-catalytic nucleotide binding sites of CF1 ATPase and inhibit ATP hydrolysis.
abstract: Guanosine triphosphate and formycin triphosphate (FTP) in the presence of excess Mg2+ can bind to empty non-catalytic sites of spinach chloroplast ATPase (CF1). This results in a greatly reduced capacity for ATP hydrolysis compared to the enzyme with non-catalytic sites filled with ATP. With two GTP bound at non-catalytic sites the inhibition is about 90%; with two FTP bound about 80% inhibition is obtained. Binding and release of the nucleotides from the non-catalytic sites are relatively slow processes. Exposure of CF1 with one or two empty non-catalytic sites to 5-10 microM FTP or GTP for 15 min suffices for about 50% of the maximum inhibition. Reactivation of CF1 after exposure to higher FTP or GTP concentrations requires long exposure to 2 microM EDTA. The findings show that, contrary to previous assumptions, GTP can bind tightly to non-catalytic sites of CF1. They suggest that the presence of adenine nucleotides at non-catalytic sites might be essential for high catalytic capacity of the F1 ATPases.
authors: Department of Chemistry and Biochemistry and Molecular Biology Institute, University of California, Los Angeles 90024.
authors: K J
authors: KJ
authors: Guerrero
authors: L L
authors: LL
authors: Ehler
authors: P D
authors: PD
authors: Boyer
mesh_terms: D000244:Adenosine Diphosphate / Q000502:physiology; D000255:Adenosine Triphosphate / Q000378:metabolism; D001639:Bicarbonates; D001665:Binding Sites; D002118:Calcium / Q000502:physiology; D002736:Chloroplasts / Q000201:enzymology*; D005573:Formycins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006358:Hot Temperature; D007700:Kinetics; D008274:Magnesium / Q000502:physiology; D010944:Plants / Q000201:enzymology; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors*; D012265:Ribonucleotides / Q000378:metabolism*
chemical_list: D001639:Bicarbonates; D005573:Formycins; D012265:Ribonucleotides; C032552:formycin triphosphate; D000244:Adenosine Diphosphate; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases; D008274:Magnesium; D002118:Calcium