title: Tentoxin. An uncompetitive inhibitor of lettuce chloroplast coupling factor 1.
abstract: The interaction of tentoxin [cyclo-(-L-leucyl-N-methyl-(Z)-dehydrophenylalanyl-glycyl-N-methyl-L-alanyl-)] with solubilized lettuce chloroplast coupling factor 1 was characterized by direct binding studies, measurement of the time course of ATPase inhibition, and steady-state enzyme kinetics. Neither substrates, products or Ca2+ competed with the tentoxin binding site, nor did they induce any large change in tentoxin affinity. The inhibition of lettuce chloroplast coupling factor 1 ATPase was found to be the time dependent, and at equilibrium the affinities estimated by equilibrium ultrafiltration and enzyme inhibition were similar (1.8 . 10(8) M-1). The steady-state kinetics best fit an uncompetitive pattern suggesting that the inhibited steps follow an irreversible step occurring after ATP binding.
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000494:pharmacology; D001665:Binding Sites; D002118:Calcium / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D007700:Kinetics; D009183:Mycotoxins / Q000494:pharmacology*; D010456:Peptides, Cyclic / Q000494:pharmacology; D010785:Photophosphorylation; D010944:Plants; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D014357:Trypsin
chemical_list: D009183:Mycotoxins; D010456:Peptides, Cyclic; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D014357:Trypsin; D000251:Adenosine Triphosphatases; D006180:Proton-Translocating ATPases; C003384:tentoxin; D002118:Calcium