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Solution structure of cytochrome c 6 from the thermophilic cyanobacterium Synechococcus elongatus
Author(s) -
Beißinger Martina,
Sticht Heinrich,
Sutter Martin,
Ejchart Andrzej,
Haehnel Wolfgang,
Rösch Paul
Publication year - 1998
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/17.1.27
Subject(s) - biology , art history , art
Cytochrome c 6 is a small, soluble electron carrier between the two membrane‐bound complexes cytochrome b 6 f and photosystem I (PSI) in oxygenic photosynthesis. We determined the solution structure of cytochrome c 6 from the thermophilic cyanobacterium Synechococcus elongatus by NMR spectroscopy and molecular dynamics calculations based on 1586 interresidual distance and 28 dihedral angle restraints. The overall fold exhibits four α‐helices and a small antiparallel β‐sheet in the vicinity of Met58, one of the axial heme ligands. The flat hydrophobic area in this cytochrome c 6 is conserved in other c 6 cytochromes and even in plastocyanin of higher plants. This docking region includes the site of electron transfer to PSI and possibly to the cytochrome b 6 f complex. The binding of cytochrome c 6 to PSI in green algae involves interaction of a negative patch with a positive domain of PSI. This positive domain has not been inserted at the evolutionary level of cyanobacteria, but the negatively charged surface region is already present in S.elongatus cytochrome c 6 and may thus have been optimized during evolution to improve the interaction with the positively charged cytochrome f . As the structure of PSI is known in S.elongatus , the reported cytochrome c 6 structure can provide a basis for mutagenesis studies to delineate the mechanism of electron transfer between both.