RELATIONSHIP BETWEEN THE RELEASE OF POLYPEPTIDES AND INHIBITION OF PHOTOSYSTEM-II ELECTRON-TRANSPORT BY RUTHENIUM RED

The dye ruthenium red has been shown to inhibit photosinthetic electron transport in photosystem II submembrane factions. It affects specifically Ca2+ and/or Cl--sensitive sites associated with the Ca2+ and Cl- requirement for oxygen evolution. In this study, it is observed that the inhibitor also causes the complete release of a 16-kDa polypeptide and the partial release of a 24-kDa polypeptide, both extrinsic proteins involved in oxygen evolution. It is shown that the release of polypeptides occurs at much lower ruthenium red concentrations than does inhibition of electron transport. It is proposed that these two events might be associated with the binding of the inhibitor on various Ca2+ sites on the donor side of the photosystem.