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 sulfate, chloroplast membranes of tobacco [Nicotiana tabacum] were separated by polyacrylamide gel electrophoresis into 3 chlorophyll-protein complexes. In addition to the 2 major complexes termed I and IIc corresponding respectively to P700 chlorophyll a-protein and light-harvesting chlorophyll a/b-protein described by Thornber, a relatively stable complex termed IIa was observed. This new complex has an apparent MW of 70,000 daltons and possesses Chl a and b. Complexes I, IIa and IIc were isolated and precise spectroscopic analyses were performed. Fourth derivative analyses of low temperature absorption spectra suggest that complex IIa seems more representative than IIc of chlorophyll a forms present in intact thylakoid membranes. The electrophoretic study reveals that CPI and CPII are composed of only 1 polypeptidic subunit with respective MW of 68,000 and 24,000 daltons.