Protein Subunits of Bacteriochlorophylls B 802 and B 855 of the Light-Harvesting Complex II of Rhodopseudomonas capsulata

Abstract

Abstract The light-harvesting antenna complex II of Rhodopseudomonas capsulata is characterized by two prominent IR-absorption maxima at 802 and 855 nm and three polypeptides of 14,000, 10,000 and 8,000 molecular weight (SDS-polyacrylamide gel electrophoresis). Bacteriochlorophyll (Bchl) is associated with the two lower molecular weight polypeptides. The membranes of the mutant Y 5, which lades reaction center and light harvesting complex I (B 875), were treated with trypsin. The 14,000 polypeptide was rapidly digested by trypsin, but the absorption spectrum of the membrane and the activity of the cytochrome c oxidase were not altered. Subsequently the 8,000 polypeptide was degraded. The digestion of the 8,000 polypeptide was concomitant with and proportional to the loss of absorbance at 802 nm. The absorption peak at 855 nm and the content of the 10,000 molecular weight polypeptide were, in contrast, stable for a longer time, but were also lost simultaneously.These results, in combination with the recent publications of Sauer and Austin (Biochemistry 17, 2011, 1978), and Cogdell and Crofts (Biochim. Biophys. Acta 502, 409, 1978) support the idea that the two molecules of Bchl associated with the 10,000 polypeptide are responsible for the 855 nm peak while the one or two mol of Bchl associated with 8,000 polypeptide result in the 802 nm absorption maximum.