Does the B820 Subcomplex of the B880 Complex Retain Carotenoids?

Andrey Moskalenko, Olga Toropygina and Nina Kuznetsova Institute of Soil Science and Photosynthesis RAS, Pushchino, 142292, Russia Z. Naturforsch. 51c, 309-318 (1996); received D ecem ber 12, 1995/February 8, 1996 Purple Bacteria, Light-Harvesting Complex, B880, B820, D issociation, Transform ation, C arotenoid A study is reported on the modification of the B880-RC assembly of Chromatium minutissimum during octyl-ß-D-glucopyranoside/dodecyl-ß-D-m altoside/Deriphat polyacrylam ide gel electrophoresis followed by electroelution with dodecyl-ß-D-maltoside and high perform ance liquid chrom atography with octyl-ß-D-glucopyranoside according to the m ethod developed by Kerfeld et al. (Biochim. Biophys. A cta 1185, 193-202 [1994a]) for isolation of the B820 subcomplexes of Chromatium purpuratum. The B880-RC assembly of Chromatium minutissimum isolated by electrophoresis was contam inated by the B 800-850 complex. It was further separated into four components, three of which were in agreem ent with the cited work: (i) colorless contam inations, (ii) the B880-RC assembly, (iii) the B 800-850 complex. In contrast with Kerfeld et al. (1994a), the fourth band was a band of free pigm ents (Bchl or Bchl-t-carotenoids) which had the sam e molecular mass as the B820 subcom plex of Chro­ matium purpuratum. For comparison, the B880-RC enriched fraction of Rhodospirillum rubrum modified by lyophilization in the presence of octyl-ß-D-glucopyranoside with or w ithout carotenoids was separated by high perform ance liquid chrom atography with octyl-ß-D-glucopyranoside. The apparent m olecular mass of the B820 subcom plex was 30 kD a for the sam ple w ithout caro t­ enoids and 245 kD a for that with carotenoids. The comm on principles of organization of the B880 complex, the interaction of the B 800850 complex with the B880-RC assembly, the participation of carotenoids in the stabilization of the B880 complex structure and the ability of different isolation steps to modify the struc­ ture of the B880 complex are discussed. It was concluded that there are o ther explanations for the presence of carotenoids in the B820 subcomplex. Hence, the question of w hether the B820 subcomplex retains carotenoids rem ains open.