Document Detail

Mechanism of enhanced superoxide production in the cytochrome b(6)f complex of oxygenic photosynthesis.
MedLine Citation:
PMID:  24298890     Owner:  NLM     Status:  MEDLINE    
The specific rate of superoxide (O2(•-)) production in the purified active crystallizable cytochrome b6f complex, normalized to the rate of electron transport, has been found to be more than an order of magnitude greater than that measured in isolated yeast respiratory bc1 complex. The biochemical and structural basis for the enhanced production of O2(•-) in the cytochrome b6f complex compared to that in the bc1 complex is discussed. The higher rate of superoxide production in the b6f complex could be a consequence of an increased residence time of plastosemiquinone/plastoquinol in its binding niche near the Rieske protein iron-sulfur cluster, resulting from (i) occlusion of the quinone portal by the phytyl chain of the unique bound chlorophyll, (ii) an altered environment of the proton-accepting glutamate believed to be a proton acceptor from semiquinone, or (iii) a more negative redox potential of the heme bp on the electrochemically positive side of the complex. The enhanced rate of superoxide production in the b6f complex is physiologically significant as the chloroplast-generated reactive oxygen species (ROS) functions in the regulation of excess excitation energy, is a source of oxidative damage inflicted during photosynthetic reactions, and is a major source of ROS in plant cells. Altered levels of ROS production are believed to convey redox signaling from the organelle to the cytosol and nucleus.
Danas Baniulis; S Saif Hasan; Jason T Stofleth; William A Cramer
Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2013-12-06
Journal Detail:
Title:  Biochemistry     Volume:  52     ISSN:  1520-4995     ISO Abbreviation:  Biochemistry     Publication Date:  2013 Dec 
Date Detail:
Created Date:  2013-12-17     Completed Date:  2014-03-03     Revised Date:  2014-05-29    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  United States    
Other Details:
Languages:  eng     Pagination:  8975-83     Citation Subset:  IM    
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MeSH Terms
Cytochrome b6f Complex / chemistry*,  metabolism*
Models, Molecular
Oxygen / metabolism*
Protein Conformation
Saccharomyces cerevisiae / enzymology,  metabolism*
Superoxides / chemistry,  metabolism*
Grant Support
Reg. No./Substance:
11062-77-4/Superoxides; 9035-40-9/Cytochrome b6f Complex; S88TT14065/Oxygen

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