INHIBITION OF OXYGEN EVOLUTION IN CHLOROPLAST PHOTOSYSTEM II BY THE PROTEIN-MODIFYING AGENT TETRANITROMETHANE

— The protein-modifying agent tetranitromethane (TNM) reacts with tyrosine residues and -SH groups. It was found to inhibit photo synthetic electron transport on the water splitting side of photosystem II (P. V. Sane and U. Johanningmeier, Z. Naturforsch. 35c, 293–297, 1979). In the present work the inhibition by TNM is studied in detail using photosystem II submembrane fractions. It is shown that the action of TNM with membrane-bound proteins could imply the modification of tyrosine residues. At concentrations below 30 μM and with short incubation periods (