Solution-state (15)N NMR spectroscopic study of alpha-C-phycocyanin: implications for the structure of the chromophore-binding pocket of the cyanobacterial phytochrome Cph1.
The detailed structure of the chromophore-binding pocket in phytochrome proteins and the structural changes associated with its photocycle are still matters of debate. Insight into the structure and dynamics of the binding pocket has been gained through the comparison of a (15)N NMR spectrum of alpha-C-phycocyanin, which is often used as a model system for the study of phytochromes, with the previously described (15)N NMR spectrum of the cyanobacterial phytochrome Cph1. The former spectrum supports the hypothesis that all four nitrogen atoms of the alpha-C-phycocyanin chromophore are protonated, in analogy with the proposed protonation state for the P(r) and P(fr) forms of Cph1. The spectra show that the chromophores in both proteins exhibit a distinct dynamic behavior, as also indicated by a NOESY spectrum of Cph1. Finally, stereochemical arguments and a Cph1 homology model support the hypothesis that the chromophore in Cph1 is most likely in the ZZZssa conformation in the P(r) form of the protein.
Hahn
Janina
J
Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Strasse 10, 13125 Berlin, Germany.
Kühne
Ronald
R
Schmieder
Peter
P
D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D000458:Cyanobacteria; D009682:Magnetic Resonance Spectroscopy; D008954:Models, Biological; D008958:Models, Molecular; D015394:Molecular Structure; D009587:Nitrogen Isotopes; D020283:Photoreceptors, Microbial; D010798:Phycocyanin / Q000737:chemistry* / Q000378:metabolism; D010834:Phytochrome / Q000737:chemistry* / Q000378:metabolism; D011494:Protein Kinases / Q000737:chemistry* / Q000378:metabolism; D012015:Reference Standards; D012996:Solutions / Q000737:chemistry
D001426:Bacterial Proteins; D009587:Nitrogen Isotopes; D020283:Photoreceptors, Microbial; D012996:Solutions; D010798:Phycocyanin; D010834:Phytochrome; D011494:Protein Kinases; C413623:Cph1 phytochrome protein, bacteria