Adjustment of conformational flexibility is a key event in the thermal adaptation of proteins

Péter Závodszky, József Kardos, Ádám Svingor, Gregory A. Petsko

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3-Isopropylmalate debydrogenase (IPMDH, E.C. from the thermophilic bacterium Thermus thermophilus HB8 is homologous to IPMDH from the mesophilic Escherichia coli, but has an approximately 17°C higher melting temperature. Its temperature optimum is 22-25°C higher than that of the E. coli enzyme; however, it is hardly active at room temperature. The increased conformational rigidity required to stabilize the thermophilic enzyme against heat denaturation might explain its different temperature- activity profile. Hydrogen/deuterium exchange studies were performed on this thermophilic-mesophilic enzyme pair to compare their conformational flexibilities. It was found that Th. thermophilus IPMDH is significantly more rigid at room temperature than E. coli IPMDH, whereas the enzymes have nearly identical flexibilities under their respective optimal working conditions, suggesting that evolutionary adaptation tends to maintain a 'corresponding state' regarding conformational flexibility. These observations confirm that conformational fluctuations necessary for catalytic function are restricted at room temperature in the thermophilic enzyme, suggesting a close relationship between conformational flexibility and enzyme function.

Original languageEnglish
Pages (from-to)7406-7411
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number13
Publication statusPublished - Jun 23 1998

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