Fast oxygen‐independent degradation of the DI reaction center protein in photosystem II

Abstract
The DI reaction center protein in photosystem II is rapidly degraded during illumination of chloride‐depleted or Tris‐washed thylakoids. The degradation is independent of oxygen and occurs under anacrobic conditions provided that electrons can flow through the acceptor‐side of photosystem II. This shows that oxygen‐derived reactive species are not necessarily involved in the light‐dependent damage of the DI protein. Instead the illumination of chloride‐depleted or Tris‐washed thylakoids induces long‐lived, strongly oxidizing radicals on the donor‐side of photosystems II which are suggested to be the damaging species for the DI protein.