Biochemical Analysis of the PGR5 Protein which is Essential for the PSI Cyclic Electron Transport.

Abstract

PGR5 (proton gradient reguleation) was found as an essential factor for the PSI cyclic electron transport from the analysis of the Arabidopsis mutants (Munekage Y. et al.(2002) Cell 110(3):361-371). However, the biochemical property and the actual function of this protein is not known at all. To tackle the function of this protein, we have investigated the exact N-terminal sequence of the mature PGR5 protein, and the localization of the protein in the chloroplasts. In addition, we analyzed the composition of the membrane protein complexes on the thylakoid membrane using the sucrose-density gradient centrifugation to determine which complex in thylakoids is functionally associated with PGR5.