ELECTROPHORETIC AND SPECTROPHOTOMETRIC STUDIES OF CHLOROPHYLL-PROTEIN COMPLEXES FROM TOBACCO CHLOROPLASTS. ISOLATION OF A LIGHT HARVESTING PIGMENT PROTEIN COMPLEX WITH A MOLECULAR WEIGHT OF 70,000

Abstract— …After a short-term solubilization with sodium dodecyl sulphate, chloroplast membranes of tobacco were separated by polyacrylamide gel electrophoresis into three chlorophyll-protein complexes. In addition to the two major complexes termed I and II_c corresponding respectively to P700 chlorophyll a -protein and light-harvesting chlorophyll a/b -protein described by Thornber (1975), a relatively stable complex termed II_a has been observed. This new complex has an apparent molecular weight of 70,000 daltons and possesses Chl a and b.
Complexes I, II_a and II_C have been isolated and precise spectroscopic analyses have been performed. Fourth derivative analyses of low temperature absorption spectra suggest that complex II_a seems more representative than II_C of chlorophyll a forms present in intact thylakoid membranes.
Moreover, the electrophoretic study reveals that CP_I and CP_II are composed of only one polypeptidic subunit with respective molecular weights of 68,000 and 24,000 daltons.