TAILIEUCHUNG - Báo cáo Y học: Purification, crystallization, NMR spectroscopy and biochemical analyses of a-phycoerythrocyanin peptides

Thea-phycoerythrocyanin subunits of the different phy-coerythrocyanin complexes of the phycobilisomes from the cyanobacterium Mastigocladus laminosusperform a remarkable photochemistry. Similar to phytochromes – the photoreceptors of higher plants – the spectral pro-perties of the molecule reversibly change according to the irradiation wavelength. To enable extensive analyses,the protein has been produced at high yield by improving purification protocols. | Eur. J. Biochem. 269 5046--5055 2002 FEBS 2002 doi Purification crystallization NMR spectroscopy and biochemical analyses of a-phycoerythrocyanin peptides Georg Wiegand1 Axel Parbel2 Markus H. J. Seifert1 Tad A. Holak1 and Wolfgang Reuter1 1 Max-Planck-Institut fur Biochemie Martinsried Germany 2Botanisches Institut der Ludwig-Maximilians-Universitat MUnchen Germany The a-phycoerythrocyanin subunits of the different phy-coerythrocyanin complexes of the phycobilisomes from the cyanobacterium Mastigocladus laminosus perform a remarkable photochemistry. Similar to phytochromes -the photoreceptors of higher plants - the spectral properties of the molecule reversibly change according to the irradiation wavelength. To enable extensive analyses the protein has been produced at high yield by improving purification protocols. As a result several comparati ee studies on the Z- and E-configurations of the intact a-subunit and also on photoactive peptides originating from nonspecific degradations of the chromoprotein were possible. The analyses comprise absorbance Ucoheshenhe and CD spectroscopy 078 111 100 preliminary X-ray measurements mass spectl ometl y. N-terminai ammo acid sequencing and 1D NMR spectroscopy. Intact a-phyco-erythrocyanin aggregates significantly due to hydrophobic interactions between the two N-terminal helices. Removal of these helices reduces the aggregation but also desta-bili1es the protein fold. The complete subunit could be crystalli1ed in its E-configuration but the y-ray measurement conditions must be improved. Nevertheless NMR spectroscopy on a soluble photoactive peptide presents the first insight into the complex chromophore protein interactions that are dependent on the light induced state. The chromophore environment in the Z-configuration is rigid whereas other regions of the protein are more flexible. In contrast the E-configuration has a mobile chromophore especially the pyrrole ring D while other regions .

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