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RESEARCH PRODUCT

Chlorophyll-Protein Complexes of Chlorella fusca

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Chlorophyll-protein complexes from thylakoids of the normal type and two mutants of Chlorella fusca were separated using sodium dodecyl sulfate acrylamide gel electrophoresis (PAGE). The properties of the chlorophyll-protein complexes of the three strains of Chlorella were compared. Standard curves were set up for the characterization of the chlorophyll-proteins. In every electrophoretic separation of chlorophyll-protein complexes, a certain amount of pigment is separated from the protein. We tried to keep that amount as low as possible by mild solubiliza­tion and by working in low temperature. Under these conditions, we obtained several new chlorophyll-proteins in addition to the P-700-chlorophyll a-protein (CP I) and the light-harvesting chlorophyll a/b-protein (CP II). Thus, a small band (CP I a) was located between the top of the gel and the CPI after elec­trophoresis. Although it shows spectral qualities similar to CP I, it possesses a much lower chloro­phyll a/chlorophyll b ratio. It may be an aggregate of photosystem I and light-harvesting chloro­phyll. We found and analyzed three other chlorophyll-proteins with electrophoretic mobilities inter­mediate between that of the P-700-chlorophyll a-protein and that of the light-harvesting chloro­phyll a/b-protein complex. Two of these chlorophyll-proteins, the LHCP1 and the LHCP2, have a low chlorophyll a/chlorophyll b ratio and spectral properties similar to that of the light-harvesting chlorophyll a/b-protein (LHCP3). They obviously represent dimers or oligomers of the latter com­plex. A third, new complex (CPa) migrated between LHCP3 and its dimer. With the chlorophyll b deficient mutant G 36 of Chlorella fusca, this complex could be obtained in high purity and great enrichment (15% of total chlorophyll). It could be proved that this complex only contains chloro­phyll a. Its red absorption maximum is at 671 nm. Some indirect evidences suggest that it may be a good candidate for the PS II reaction center complex.