Sulphydryl groups in photosynthetic energy conservation. IV. Inhibition of the ATPase of chloroplast coupling factor 1 by sulphydryl reagents.
1. O-Iodosobenzoate and 2,2'-dithio bis-(5-nitropyridine) inhibited by about fifty per cent the ATPase activity of heat-activated chloroplast coupling factor 1 only when present during the heating but were without effect when added before or after the activation. Reversion of this inhibition was only obtained by a second heat treatment with 10 mM dithioerythritol. 2. The inhibition of the Ca2+-ATPase of coupling factor 1 by o-iodosobenzoate or 2,2'-dithio bis-(5-nitropyridine) was not additive with similar inhibitions obtained with the alkylating reagents iodoacetamide and N-ethylmaleimide. 3. The heat-activated ATPase of o-iodosobenzoate-treated coupling factor 1 had a higher Km for ATP, without modification of V. The modified enzyme was desensitized against the allosteric inhibitor ADP.
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D002736:Chloroplasts / Q000187:drug effects / Q000201:enzymology*; D004220:Disulfides / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D007463:Iodobenzoates / Q000494:pharmacology*; D007700:Kinetics; D009574:Nitro Compounds / Q000494:pharmacology*; D010788:Photosynthesis / Q000187:drug effects*; D010940:Plant Proteins / Q000378:metabolism*; D010944:Plants; D011725:Pyridines / Q000494:pharmacology*
D004220:Disulfides; D007463:Iodobenzoates; D009574:Nitro Compounds; D010940:Plant Proteins; D011725:Pyridines; D000251:Adenosine Triphosphatases; D002118:Calcium