Institution: | a Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, U.S.A. b Exxon Research and Engineering Company, Annandale, NJ, U.S.A. c Institute of Biology, University of Regensburg, Regensburg, F.R.G. |
Abstract: | MT113, a nonphotosynthetic mutant of Rhodobacter capsulatus previously characterized as lacking cytochrome c2 is shown to lack also cytochrome c1, the Rieske iron-sulfur cluster and the antimycin sensitive semiquinone Q c, all components of the cytochrome bc1 complex. Although MT113 contained b-type cytochromes and other iron-sulfur clusters at nearly wild-type level, it lacks c-type cytochromes. Based on antibody detection, c2 apoprotein was absent in MT113, however the apoproteins corresponding to the cytochromes b and c1 and the Rieske iron-sulfur cluster were present in reduced amounts. Genetic analysis indicated that the lesion appears to be due to a single mutation which is not localized in the structural genes of cytochrome c2 or the bc1 complex. These data taken together suggest that the pleiotropic mutation in MT113 might be related to the biosynthesis of c-type cytochromes. |