Turnover of the B870-α pigment-binding protein in a mutant ofRhodopseudomonas capsulatawhich is defective in assembling reaction center and B870 into membranes

The photosynthetically negative mutant strain Y142 of Rhodopseudomonas capsulata, which synthesizes bacteriochlorophyll (Bchl), carotenoids and the light-harvesting (LH) complex B800–850, but no reaction center and LH complex B870, is capable of synthesizing the Bchl-binding polypeptide (α, 12 kDa) of B870. In contrast to the high stability of the polypeptides of the B800–850 complex, the 12 kDa polypeptide was rapidly degraded after synthesis and insertion into the membrane.