TAILIEUCHUNG - Báo cáo khoa học: Unfolding process of rusticyanin Evidence of protein aggregation

The unfolding process of the Blue Copper Protein (BCP) rusticyanin (Rc) has been studied using a wide variety of biochemical techniques. Fluorescence and CD spectroscop-ies reveal that the copper ion plays an essential role in sta-bilizing the protein and that the oxidized form is more efficient than the reducedspecies in this respect. Theaddition of guanidinium chloride to Rc samples produces aggrega-tion of the protein. Gel filtration chromatography and glutaraldehyde cross-linking experiments confirm the for-mation of such aggregates. . | Eur. J. Biochem. 271 4284-4292 2004 FEBS 2004 doi Unfolding process of rusticyanin Evidence of protein aggregation Luis A. Alcaraz and Antonio Donaire Instituto de Biologia Molecular y Celular Universidad Miguel Hernandez Spain The unfolding process of the Blue Copper Protein BCP rusticyanin Rc has been studied using a wide variety of biochemical techniques. Fluorescence and CD spectroscopies reveal that the copper ion plays an essential role in stabilizing the protein and that the oxidized form is more efficient than the reduced species in this respect. The addition of guanidinium chloride to Rc samples produces aggregation of the protein. Gel filtration chromatography and glutaraldehyde cross-linking experiments confirm the formation of such aggregates. Among the BCPs this feature is exclusive to Rc. The aggregation could be related to the large molecular mass and large number of hydrophobic residues of this protein compared with those of other BCPs. Keywords aggregation Blue Copper Protein metaloprotein protein unfolding rusticyanin. An understanding of folding processes is crucial in order to determine the causes of protein stability 1-4 . Small proteins typically unfold by means of a simple two-state mechanism characterized by the absence of intermediates between the two extreme folded and unfolded states. The process is usually cooperative reflecting the complementary nature of the tertiary interactions that maintain the protein scaffold. With larger proteins the mechanism is more complex and intermediate usually molten globule species appear 5-7 . The existence of these states is relevant in many biological processes such as expression of proteins their translocation across membranes and the possible formation of amyloids which in turn are responsible for several neurodegenerative diseases 4 8 9 . Thus exhaustive efforts to understand how these intermediates are formed and their role in protein folding are being made 6 10 11

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