Evidence for an association of the early light-inducible protein (ELIP) of pea with photosystem II.

The precursor to the nuclear-coded 17 kDa early light-inducible protein (ELIP) of pea has been transported into isolated intact chloroplasts. The location of the mature protein in the thylakoid membranes was investigated after using cleavable crosslinkers such as DSP and SAND in conjunction with immunofractionation methods and by application of mild detergent fractionation. We show that ELIP is integrated into the membranes via the unstacked stroma thylakoids. After isolation of protein complexes by solubilization of membranes with Triton X-100 and sucrose density-gradient centrifugation the crosslinked ELIP comigrates with the PS II core complex. Using SAND we identified ELIP as a 41-51 kDa crosslinked product while with DSP four products of 80 kDa, 70 kDa, 50-42 kDa and 23-21 kDa were found. The immunoprecipitation data suggested that the D1-protein of the PS II complex is one of the ELIP partners in crosslinked products.