Study of vanadate as a photosensitizer and kinetic inhibitor of beef heart mitochondrial F1-ATPase

TL;DRAbstract

The ability of vanadate to act as a photosensitizing agent and also as an inhibitor of the function of beef heart mitochondria1 F1-ATPase was investigated.Vanadate-sensitized photoinactivation of F l was biphasic with a fast rate of inactivation followed by a less sensitive phase.Monovanadate was found to be the species interacting with F1 during the photoinactivation process with a Ki of 12.3 + 0.9 pM.ADP and PPi both diminished Pi binding and Vi binding to the enzyme.ADP protected F1 from photoinactivation whereas PPi at concentration below 120 pM enhanced the process, but reduced the extent of photoinactivation when present in higher concentration.Pi at high concentration did not prevent vanadate-sensitized photoinactivation.Vanadate inhibited 3 2 ~ [ ~i ] binding to F1 but not completely.These results suggest that Pi and Vi can bind simultaneously to the protein, and that the protein is sensitized to photoinactivation when both ligands are bound.Electrophoresis of photoinactivated

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