TAILIEUCHUNG - Báo cáo Y học: Stepwise adaptations of citrate synthase to survival at life’s extremes From psychrophile to hyperthermophile

The crystal structure of citrate synthase from the thermo-philic ArchaeonSulfolobus solfataricus(optimum growth temperature ¼85 C) has been determined, extending the number of crystal structures of citrate synthase from differ-ent organisms to a total of five that span the temperature range over which life exists (from psychrophile to hyper-thermophile). Detailed structural analysis has revealed possible molecular mechanisms that determine the different stabilities of thefiveproteins. | Eur. J. Biochem. 269 6250-6260 2002 FEBS 2002 doi Stepwise adaptations of citrate synthase to survival at life s extremes From psychrophile to hyperthermophile Graeme S. Bell1 Rupert J. M. Russell2 Helen Connaris2 David W. Hough1 Michael J. Danson1 and Garry L. Taylor1 2 1 Centre for Extremophile Research Department of Biology and Biochemistry University of Bath UK 2Centre for Biomolecular Sciences University of St Andrews St. Andrews UK The crystal structure of citrate synthase from the thermophilic Archaeon Sulfolobus solfataricus optimum growth temperature 85 C has been determined extending the number of crystal structures of citrate synthase from different organisms to a total of five that span the temperature range over which life exists from psychrophile to hyperthermophile . Detailed structural analysis has revealed possible molecular mechanisms that determine the different stabilities of the five proteins. The key to these mechanisms is the precise structural location of the additional interactions. As one ascends the temperature ladder the subunit interface of this dimeric enzyme and loop regions are reinforced by complexelectrostatic interactions and there is a reduced exposure of hydrophobic surface. These observations reveal a progressive pattern of stabilization through multiple additional interactions at solvent exposed loop and interfacial regions. Keywords citrate synthase Sulfolobus citrate synthase thermostability crystal structure ion networks. Comparative structural analysis of the same protein isolated from mesophiles and thermophiles have highlighted many structural adaptations that confer protein thermostability 1-6 . The importance of electrostatic interactions at specific locations within the structure and particularly the presence of ion-pair networks is a feature that is common to almost all the hyperthermophilic proteins 7-10 although many other additional differences such as improved hydrophobic packing

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