Resonance Raman evidence for two conformations involved in the L intermediate of photoactive yellow protein.
The blue light receptor photoactive yellow protein (PYP) displays a photocycle that involves several intermediate states. Here we report resonance Raman spectroscopic investigations of the short-lived red-shifted intermediate denoted PYP(L). We have found that the Raman bands of the carbonyl C=O stretching mode nu(11) as well as the C=C stretching mode nu(13) for the chromophore can be resolved into two peaks, and the ratio of the two components varies as a function of pH with pK(a) approximately 6. The isotope effects on the resonance Raman spectra have confirmed a deprotonated cis-chromophore for the two components. The results indicate the presence of two conformations in the active site of PYP(L). The normal coordinate calculations based on the density functional theory provide a structural model for the two conformations, where the low pH form is possibly an active structure for the protonation reaction generating a following intermediate in the photocycle.
Unno
Masashi
M
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan. unno@tagen.tohoku.ac.jp
Kumauchi
Masato
M
Hamada
Norio
N
Tokunaga
Fumio
F
Yamauchi
Seigo
S
D001426:Bacterial Proteins / Q000737:chemistry*; D001665:Binding Sites; D002841:Chromatiaceae; D020607:Halorhodospira halophila / Q000378:metabolism; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008027:Light; D008956:Models, Chemical; D008968:Molecular Conformation; D009154:Mutation; D019800:Phenol / Q000737:chemistry; D020283:Photoreceptors, Microbial / Q000737:chemistry*; D011487:Protein Conformation; D011506:Proteins; D011522:Protons; D013059:Spectrum Analysis, Raman / Q000379:methods*; D014732:Vibration
D001426:Bacterial Proteins; D020283:Photoreceptors, Microbial; D011506:Proteins; D011522:Protons; C050162:photoactive yellow protein, Bacteria; D019800:Phenol