PIGMENT-PROTEIN COMPLEXES FROM CHROMATIUM-MINUTISSIMUM AFTER EXTRACTION OF CAROTENOIDS

Up to 50% of carotenoids were selectively extracted with benzene from the membranes of Chromatium minutissimum. Extraction of carotenoids di d not influence the spectral properties of the membranes. These membra nes treated with n-octyl glucoside (OG)(3) were separated by PAGE into three bands, which represented: 1) partially destroyed B880-RC assemb ly with preserved carotenoids which limited the dissociation of B880 c omplex into subunits; 2) a new blue band which is the carotenoid-free B812 subcomplex (a subunit of the B880 complex) according to spectral characteristics and polypeptide composition. The re-associated B812 co mplex, as compared to the analogous complex from non-sulfur bacteria, revealed unusual properties: appearance of two forms of bacteriochloro phyll (Bchl) at 796 nm and 845-847 nm, absence of fluorescence of the two forms of Bchl, stability in the presence of ionic detergents; 3) l ight-harvesting B800-B850 complex, partially depleted of carotenoids ( up to 40%). Larger conformational changes were characteristic of this complex in the presence of non-ionic detergent as compared to the cont rol.