A Photosystem II light-harvesting chlorophyll-protein complex with a high fluorescence emission at 736 nm

Abstract

A light-harvesting chlorophyll—protein complex (LHC-II) with a high fluorescence emission at 736 nm (77 K) was prepared from spinach thylakoids using a modification of the purification method for LHC-II described previously (Ryrie et al. (1980) Eur. J. Biochem. 107, 345). The principal modification was the use of low (0-4°C) temperatures during the solubilization and Mg 2 ‘-induced aggregation steps. Photosystem I (PSI) contamination of this LHC-II preparation was judged most unlikely to be responsible for the 736 nm fluorescence on the basis of chlorophyll a/b ratios, protein/chlorophyll ratios, lack of P-700, no detectable PSI electron transport activity, and polypeptide analysis with SDS-urea polyacrylamide gel electrophoresis. We suggest that the fluorescence emission at 736 nm is an inherent property of LHC-II, but is destroyed during preparation of the complex at room temperature.