The influence of bacteriochlorophyll biosynthesis on formation of pigment-binding proteins and assembly of pigment protein complexes in Rhodopseudomonas capsulata

Abstract

The synthesis of bacteriochlorophyll (Bchl) was inhibited in wild type strain of Rhodopseudomonas capsulata by levulinic acid (LA), δ-aminolevulinic acid of α,α′-dipyridyl. The transcription of genes for pigment-binding proteins, the synthesis and incorporation of these proteins into the membrane and the assembly of photosynthetic complexes were studied. Inhibition of Bchl synthesis did not impair formation of mRNA for pigment-binding polypeptides, but inhibited the synthesis of these proteins as well as stable incorporation into the membrane. The results let suggest, that Bchl is necessary for the stabilization of pigment-binding proteins in the membrane, and that intermediates of Bchl-synthesis affect the synthesis of these proteins. The same experiments were carried out with mutant strains blocked in Bchl synthesis. All Bchl-less mutant strains investigated here, showed transcription of photosynthetic genes at a rate which was independent of oxygen tension. The synthesis of polypeptides of reaction center, B870 and B800-850 complexes were differently affected by blocks in Bchl-synthesis. LA inhibited the synthesis of pigment-binding proteins in mutant strains similarly as in wild-type strain.