Document Detail

Lipid functions in cytochrome bc complexes: an odd evolutionary transition in a membrane protein structure.
MedLine Citation:
PMID:  23148267     Owner:  NLM     Status:  MEDLINE    
Lipid-binding sites and properties were compared in the hetero-oligomeric cytochrome (cyt) b(6)f and the yeast bc(1) complexes that function, respectively, in photosynthetic and respiratory electron transport. Seven lipid-binding sites in the monomeric unit of the dimeric cyanobacterial b(6)f complex overlap four sites in the Chlamydomonas reinhardtii algal b(6)f complex and four in the yeast bc(1) complex. The proposed lipid functions include: (i) interfacial-interhelix mediation between (a) the two 8-subunit monomers of the dimeric complex, (b) between the core domain (cyt b, subunit IV) and the six trans membrane helices of the peripheral domain (cyt f, iron-sulphur protein (ISP), and four small subunits in the boundary 'picket fence'); (ii) stabilization of the ISP domain-swapped trans-membrane helix; (iii) neutralization of basic residues in the single helix of cyt f and of the ISP; (iv) a 'latch' to photosystem I provided by the β-carotene chain protruding through the 'picket fence'; (v) presence of a lipid and chlorophyll a chlorin ring in b(6)f in place of the eighth helix in the bc(1) cyt b polypeptide. The question is posed of the function of the lipid substitution in relation to the evolutionary change between the eight and seven helix structures of the cyt b polypeptide. On the basis of the known n-side activation of light harvesting complex II (LHCII) kinase by the p-side level of plastoquinol, one possibility is that the change was directed by the selective advantage of p- to n-side trans membrane signalling functions in b(6)f, with the lipid either mediating this function or substituting for the trans membrane helix of a signalling protein lost in crystallization.
S Saif Hasan; William A Cramer
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural    
Journal Detail:
Title:  Philosophical transactions of the Royal Society of London. Series B, Biological sciences     Volume:  367     ISSN:  1471-2970     ISO Abbreviation:  Philos. Trans. R. Soc. Lond., B, Biol. Sci.     Publication Date:  2012 Dec 
Date Detail:
Created Date:  2012-11-13     Completed Date:  2013-04-22     Revised Date:  2014-01-10    
Medline Journal Info:
Nlm Unique ID:  7503623     Medline TA:  Philos Trans R Soc Lond B Biol Sci     Country:  England    
Other Details:
Languages:  eng     Pagination:  3406-11     Citation Subset:  IM    
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MeSH Terms
Binding Sites
Cell Membrane / metabolism
Chlamydomonas reinhardtii / metabolism
Cyanobacteria / metabolism
Cytochrome b6f Complex / metabolism*
Electron Transport
Evolution, Molecular*
Light-Harvesting Protein Complexes / metabolism
Membrane Lipids / metabolism*
Membrane Proteins / metabolism*
Photosystem I Protein Complex / metabolism
Protein Binding
Protein Stability
Protein Structure, Secondary
Protein Structure, Tertiary
Signal Transduction
Structure-Activity Relationship
Grant Support
Reg. No./Substance:
0/Light-Harvesting Protein Complexes; 0/Membrane Lipids; 0/Membrane Proteins; 0/Photosystem I Protein Complex; 9035-40-9/Cytochrome b6f Complex

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