1igk

Theoretical Model: The protein structure described on this page was determined theoretically, and hence should be interpreted with caution.

MODELED COMPLEX BETWEEN PHOTOSYSTEM II AND CYTOCHROME C549MODELED COMPLEX BETWEEN PHOTOSYSTEM II AND CYTOCHROME C549

Structural highlights For a guided tour on the structure components use FirstGlance. Resources: FirstGlance, PDBsum, ProSAT Publication Abstract from PubMed Cytochrome c(6) and cytochrome c-549 are small (89 and 130 amino acids, respectively) monoheme cytochromes that function in photosynthesis. They appear to have descended relatively recently from the same ancestral gene but have diverged to carry out very different functional roles, underscored by the large difference between their midpoint potentials of nearly 600 mV. We have determined the X-ray crystal structures of both proteins isolated from the cyanobacterium Arthrospira maxima. The two structures are remarkably similar, superimposing on backbone atoms with an rmsd of 0.7 A. Comparison of the two structures suggests that differences in solvent exposure of the heme and the electrostatic environment of the heme propionates, as well as in heme iron ligation, are the main determinants of midpoint potential in the two proteins. In addition, the crystal packing of both A. maxima cytochrome c-549 and cytochrome c(6) suggests that the proteins oligomerize. Finally, the cytochrome c-549 dimer we observe can be readily fit into the recently described model of cyanobacterial photosystem II. Structures of cytochrome c-549 and cytochrome c6 from the cyanobacterium Arthrospira maxima.,Sawaya MR, Krogmann DW, Serag A, Ho KK, Yeates TO, Kerfeld CA Biochemistry. 2001 Aug 7;40(31):9215-25. PMID:11478889 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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