Inhibition of the Mitochondrial F1-ATPase by Rose Bengal Mediated Photooxidation. Interaction of the Fe2+ Chelate of Bathophenanthroline with the Sensitizer.

Abstract

Rose Bengal mediated photooxidation of mitochondrial F1-ATPase and its .beta.-subunit resulted in inactivation and loss of about 50 and 60% of their histidine residues, respectively. The .beta.-subunit was not cleaved upon photooxidation. Photooxidation of histidine probably results in changes in the conformational stability of F1-ATPase leading to its inactivation. The participation of singlet molecular oxygen during the photooxidation process is suggested by the selective loss of histidine residues, while other amino acids, also sensitive to singlet oxygen attack, were not affected. Photochemical camge of F1-ATPase was preveted by various phenanthroline compounds, the order of efficiency being bathophenanthroline-Fe chelate > bathophenanthroline > orthophenanthroline-Fe chelate > bathophenanthroline-sulfonate-Fe chelate. The prevention by bathophenanthrone-Fe chelate of photochemical damage is interpreted on the basis of its interaction with the photosensitizer, Rose Bengal, probably implying a chemical reaction which decreases the actual concentration of the sensitizer and, thereby, the extent of photoinactivation.