On the presence and role of a molecule of chlorophyll a in the cytochrome b6 f complex.
Highly purified preparations of cytochrome b6 f complex from the unicellar freshwater alga Chlamydomonas reinhardtii contain about 1 molecule of chlorophyll a/cytochrome f. Several lines of evidence indicate that the chlorophyll is an authentic component of the complex rather than a contaminant. In particular, (i) the stoichiometry is constant; (ii) the chlorophyll is associated with the complex at a specific binding site, as evidenced by resonance Raman spectroscopy; (iii) it does not originate from free chlorophyll released from thylakoid membranes upon solubilization; and (iv) its rate of exchange with free, radioactive chlorophyll a is extremely slow (weeks). Some of the putative functional roles for a chlorophyll in the b6f complex are experimentally ruled out, and its possible evolutionary origin is briefly discussed.
Pierre
Y
Y
Institut de Biologie Physico-Chimique and Paris-7 University, CNRS UPR 9052, 13 rue Pierre et Marie Curie, F-75005 Paris, France.
Breyton
C
C
Lemoine
Y
Y
Robert
B
B
Vernotte
C
C
Popot
J L
JL
D000818:Animals; D001665:Binding Sites; D016825:Chlamydomonas reinhardtii / Q000201:enzymology* / Q000235:genetics; D002734:Chlorophyll / Q000032:analysis* / Q000378:metabolism; D000077194:Chlorophyll A; D003573:Cytochrome b Group / Q000737:chemistry* / Q000378:metabolism; D045346:Cytochrome b6f Complex; D004579:Electron Transport; D016296:Mutagenesis; D013050:Spectrometry, Fluorescence; D013054:Spectrophotometry, Atomic; D013059:Spectrum Analysis, Raman
D003573:Cytochrome b Group; D002734:Chlorophyll; D045346:Cytochrome b6f Complex; D000077194:Chlorophyll A