Studies on pigments and lipids in Rhodopseudomonas spheroides Y reaction center

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In photosynthetic bacteria light is absorbed in a set of ‘light harvesting’ pigment molecules (Bchls* and carotenoids): its energy is then transferred to special pigment complexes, called reaction centers, where the primary photochemical oxidoreduction takes place [ 1 ] . Reaction center preparations enriched in photochemical activity and devoid of light harvesting Bchl have been now isolated from various bacterial species; the best characterized to-date are from R, spheroides, especially those from a carotenoid-less mutant, R-26, obtained by extracting the membranes with LDAO [2,3]. As reported by several authors, these reaction center particles contain three polypeptide chains [4,5] and no lipids [2] : Bchl and Bpheo are present in a 2: 1 ratio [6,7]. Several arguments favor a model with 4 Bchl and 2 Bpheo by reaction center unit (see [l] ). Reaction center preparations have been obtained from wild type R. spheroides strains, by extraction with either SLS [8,9], CTAB [lo] or LDAO [ 111. In the two later cases, we have found a number of similarities with the R-26 reaction center preparations, as regard the spectral properties and the polypeptide composition [ 1 l] ; however, we noted that in the wild type preparation only, residual phospholipids and carotenoids were still present [ 1 l] . We did not determine the pigment composition; for SDS extract-