The 33 kDa subunit of Photosystem II is a GTP-binding protein -- presence of nucleotides in the thylakoid lumen

摘要

Recently, we reported in Spetea et al. (1999) that following photoinactivation of photosystem II (PSII), proteolysis of the reaction center D1 protein proceeds in at least two enzymatic steps with different nucleotide requirement. The primary proteolytic step is GTP-dependent whereas the secondary step requires ATP. The primary step was found to be associated withisolated PSII complexes. Binding of GTP to the thylakoid membrane is tight and lightdependent. In Spetea et al. (2000), we demonstrated that the role of GTP in D1 protein degradation is at the level of the proteolytic enzymes, directly or via a chain ofreactions. The concept of a more general significance for the existence of GTP tightly bound to the thylakoid membrane for regulatory reactions during photosynthesis has also been raised. In this work, we have investigated the presence of GTP-binding proteins associated with the thylakoid membrane.