Relationship between the Stability of Antenna Chl {alpha}-Binding Proteins CP43/47 and the Accumulation of the Extrinsic 30-kDa Protein in PS II in Euglena

The accumulation of the extrinsic 30-kDa protein of PS II inthylakoid membranes was studied in relation to the assemblyof PS II antenna Chl-proteins CP43/47 and light-harvesting Chia/b-protein (LHC) in greening cells of Euglena. We showed previouslythat the 30-kDa protein accumulates in the membrane later thanthe reaction center-binding Dl protein (Mizobuchi and Yamamoto1989). In the present study, the rate of accumulation of theapoproteins of LHC and CP43/47 was shown to be similar to thatof the Dl protein. By contrast, we found by non-denaturing lithiumdodecyl sulfate-polyacrylamide gel electrophoresis that, atthe early stages of greening, newly assembled antenna Chi a-bindingproteins CP43 and CP47 were more susceptible to detergent thanwere the other Chl-protein complexes. Prolonged illuminationwas required for the stabilization of CP43 and CP47, and thetime course of the light-dependent formation of stable CP43/47paralleled that of the accumulation of the extrinsic 30-kDaprotein. These results are discussed in terms of the relationshipbetween the stabilization of CP43/47 and the accumulation ofthe 30-kDa protein in the thylakoid membrane and the roles ofthese two processes in the assembly of the oxygen-evolving systemin Euglena are examined. (Received February 18, 1991; Accepted June 17, 1991)