Spectral Characterization of Five Chlorophyll-Protein Complexes

Abstract

Sodium dodecyl sulfate-solubilized chloroplast internal membranes of higher plants (cowpea [Vigna unguiculata L. Walp], chinese cabbage [Brassica chinensis L. [cv. Michili]], and tobacco [Nicotiana tabacum L. [cv. Glurk]]) are resolved by polyacrylamide gel electrophoresis into 2 chlorophyll a- and 3 chlorophyll a,b-proteins. A small portion (about 15%) of the membrane chlorophyll migrates as a component of high electrophoretic mobility and presumably consists of detergent-complexed, protein-free pigment. One of the chlorophyll a-proteins is qualitatively similar to the P700 chlorophyll a-protein but contains a much larger proportion of total chlorophyll (about 30%) than previously reported. The second chlorophyll a-protein is a recently discovered component of the membrane and accounts for about 7% of the total chlorophyll. The absorption and fluorescence emission spectra of these 2 chlorophyll a-proteins differ. The 3 chlorophyll a,b-proteins are components of the chloroplast membrane chlorophyll a,b-light-harvesting complex which was previously resolved as a single chlorophyll-protein band. The 2 additional chlorophyll a,b-proteins observed in the work probably represent larger aggregates contained within the membrane complex which are preserved under the solubilization and electrophoretic conditions used here.