Structure, Properties and Function of Photoactive Yellow Protein

点击翻译按钮获取中文摘要

We have studied intensively the structural changes upon light absorption, and searched the target molecule of PYP.1.We examined the photoreaction of PYP in a crystal, and found that the M intermediate is hardly observable in a crystal. This suggests two possibilities : no reaction is occurred in a crystal or the photoreaction accelerates extremely in a crystal. The photoreaction is significantly affected from the force constraint of crystalline lattice.2.Based on the CD measurements under illumination, we revealed that the structural changes due to M formation are composed of the loss of α-helical structure of the N-terminal region, the distortion of α-helix of C-terminal domain and the changes in β-core.3.We also revealed by solution X-ray scattering under Illumination that the C-terminal domain swells and the distance between the N-terminal region and the C-terminal domain increases upon the formation of the M intermediate.4.These structural changes are induced by the changes in the electrostatic interaction. The region from the 7th and the 15th is responsible to the Interaction.Citrate ion binds specifically to the M intermediate. One of the binding sites is found to be R52.6.Through the crystal structural analysis of R52Q, the essential water molecule that controls the pKa of the chromophore at the L formation is identified.7.The fraction that slows down the photoreaction rate was isolated from Ectothiorhodospira halophila cell. The major component is found to be a protein. The purification is now under way.8.Artificial PYP's with the simplified sequences are designed, expressed in E.coli and purified. The structures, properties and photoreactions of these simplified PYP's were examined to clarify the functional regions and structural regions.