b6f-Associated chlorophyll: structural and dynamic contribution to the different cytochrome functions.
Cytochromes bc1/b6f complexes catalyze electron transfer from lipid- to water-soluble carriers in both the respiratory and photosynthetic processes. They contain several common redox cofactors, while a chlorophyll a molecule, the function of which is still enigmatic, is only present in b b6f-type complexes. In this work, we describe a mutagenesis approach aimed at characterizing the role of this pigment. Mutants of the binding pocket were constructed to obtain cytochrome (cyt) b6f f complexes altered in chlorophyll position and/or stability. On the basis of a combined biochemical and functional analysis, we conclude that the chlorophyll plays a major structural role in the complex. Moreover, the chlorophyll and its binding pocket may also be implicated in the regulation of photosynthetic state transitions, a function that is specific to cyt b6f complexes.
de Lacroix de Lavalette
Agnès
A
UMR 7099, CNRS and Université Paris-7, and UMR 7141, CNRS and Université Paris-6, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, F-75005 Paris, France.
Finazzi
Giovanni
G
Zito
Francesca
F
D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000201:enzymology / Q000235:genetics; D002734:Chlorophyll / Q000737:chemistry* / Q000378:metabolism*; D045346:Cytochrome b6f Complex / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D010777:Photochemistry; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D021122:Protein Subunits; D002734:Chlorophyll; D045346:Cytochrome b6f Complex