Does the B820 Subcomplex of the B880 Complex Retain Carotenoids?

Abstract

Listen

Translate article

Abstract A study is reported on the modification of the B880-RC assembly of Chromatium minutissimum during octyl-β-D -glucopyranoside/dodecyl-β-D -maltoside/Deriphat polyacrylamide gel electrophoresis followed by electroelution with dodecyl-β-D-maltoside and high performance liquid chromatography with octyl-β-D-glucopyranoside according to the method developed by Kerfeld et al. (Biochim. Biophys. Acta 1185, 193-202 [1994a]) for isolation of the B820 subcomplexes of Chromatium purpuratum. The B880-RC assembly of Chromatium minutissimum isolated by electrophoresis was contaminated by the B 800-850 complex. It was further separated into four components, three of which were in agreement with the cited work: (i) colorless contaminations, (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 pigments (Bchl or Bchl-t-carotenoids) which had the same molecular mass as the B820 subcomplex of Chromatium purpuratum. For comparison, the B880-RC enriched fraction of Rhodospirillum rubrum modified by lyophilization in the presence of octyl-β-D-glucopyranoside with or w ithout carotenoids was separated by high performance liquid chromatography with octyl-β-D-glucopyranoside. The apparent molecular mass of the B820 subcomplex was 30 kD a for the sample without carotenoids and 245 kD a for that with carotenoids. The common principles of organization of the B880 complex, the interaction of the B 800- 850 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 structure of the B880 complex are discussed. It was concluded that there are other explanations for the presence of carotenoids in the B820 subcomplex. Hence, the question of whether the B820 subcomplex retains carotenoids remains open.