| Abstract: | Photophosphorylation by spinach chloroplasts is inhibited after they have been incubated in the dark with either phenylglyoxal or butanedione. Inhibition by phenylglyoxal is strongest when N-ethylmorpholine is the buffer used during the incubation; that by butanedione requires the presence of borate as buffer. The inhibitions are not reversed by simply washing out the inhibitor, suggesting that a covalent modification of one or more arginine residues is responsible. This is supported by the reversibility of the butanedione inhibition if both the inhibitor and borate buffer are removed. ATPase of the chloroplasts, and of extracted protein, is inhibited, whether activated by trypsin or by heating. This indicates that arginine residues of the coupling factor are the probable major site(s) for attack by these modifiers, leading to the observed inhibitions. |
