title: Interference of methyl trachyloban-19-oate ester with CF(0) of spinach chloroplast H(+)-ATPase.
abstract: In isolated spinach chloroplasts, low concentrations (I(50)=14 microM) of methyl trachyloban-19-oate ester inhibited ATP synthesis and coupled electron transport as well as light-activated membrane-bound Mg(2+)-ATPase activity. Basal (-Pi) and uncoupled electron transport and heat-activated Ca(2+)-dependent ATPase activity of isolated coupling factor proteins were unaffected by methyl trachyloban-19-oate. Thylakoids partially stripped of coupled factor by EDTA were unable to accumulate protons in the light. However, increasing concentrations of methyl trachyloban-19-oate ester restored this ability. It is concluded that the methyl trachyloban-19-oate ester effects result from blocking proton transport through the CF(0) channel. Methyl trachyloban-19-oate ester exhibited non-competitive kinetics with DCCD and triphenyltin. These results suggest that the natural products, DCCD and triphenyltin, access inhibition sites in CF(0). The K(i) is 75 microM.
mesh_terms: D025222:Chloroplast Proton-Translocating ATPases / Q000737:chemistry / Q000378:metabolism*; D002736:Chloroplasts / Q000737:chemistry / Q000378:metabolism*; D004024:Dicyclohexylcarbodiimide / Q000737:chemistry / Q000378:metabolism; D004224:Diterpenes / Q000737:chemistry / Q000378:metabolism*; D009947:Organotin Compounds / Q000737:chemistry / Q000378:metabolism; D018724:Spinacia oleracea / Q000737:chemistry / Q000378:metabolism*
chemical_list: D004224:Diterpenes; D009947:Organotin Compounds; C039978:trachyloban-19-oic acid; D004024:Dicyclohexylcarbodiimide; C030665:triphenyltin; D025222:Chloroplast Proton-Translocating ATPases