1. Biogenesis of cytochrome b6 in photosynthetic membranes.
- Author
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Saint-Marcoux D, Wollman FA, and de Vitry C
- Subjects
- Animals, Chlamydomonas reinhardtii cytology, Chlamydomonas reinhardtii genetics, Cytochromes b6 chemistry, Cytochromes b6 genetics, Dimerization, Electrophoresis, Membrane Proteins chemistry, Membrane Proteins genetics, Models, Molecular, Mutation, Protein Structure, Tertiary, Protozoan Proteins chemistry, Protozoan Proteins genetics, Two-Hybrid System Techniques, Ubiquitin metabolism, Chlamydomonas reinhardtii enzymology, Cytochromes b6 biosynthesis, Membrane Proteins metabolism, Protozoan Proteins biosynthesis, Thylakoids enzymology
- Abstract
In chloroplasts, binding of a c'-heme to cytochrome b(6) on the stromal side of the thylakoid membranes requires a specific mechanism distinct from the one at work for c-heme binding to cytochromes f and c(6) on the lumenal side of membranes. Here, we show that the major protein components of this pathway, the CCBs, are bona fide transmembrane proteins. We demonstrate their association in a series of hetero-oligomeric complexes, some of which interact transiently with cytochrome b(6) in the process of heme delivery to the apoprotein. In addition, we provide preliminary evidence for functional assembly of cytochrome b(6)f complexes even in the absence of c'-heme binding to cytochrome b(6). Finally, we present a sequential model for apo- to holo-cytochrome b(6) maturation integrated within the assembly pathway of b(6)f complexes in the thylakoid membranes.
- Published
- 2009
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