DATE : 2009. 9. 3, 4 :00 PM Place: Mogam Hall, Bldg 500 - Abstract - Engineering proteins for higher thermal stability remains an important but difficult challenge. Clues to designing more stable proteins can be obtained by comparing and contrasting natural proteins from thermophiles, mesophiles and psychrophiles. Three such adenylate kinases were studied to reveal sequential and structural differences responsible for their disparate thermal stabilities. To obtain detailed information about their structures and dynamics, experimental and computational techniques were used. Their crystal structures were solved by X-ray crystallography and their dynamics were studied using molecular dynamics simulations. Based on comparative analysis of the structures and simulations, specific molecular mechanisms for their different thermal stabilities were proposed and tested by in vitro and in silico analysis of mutant enzymes. To further distinguish the roles of specific structural domains in stability and catalysis of adenylate kinase, chimeric enzymes were developed from the thermophilic and mesophilic adenylate kinases. Using a new method with synthetic genes, a series of chimeras were efficiently generated with specific regions exchanged. Analysis of the chimeras revealed that stability and activity were controlled by different domains in adenylate kinase. A bioinformatic method has also been developed to redesign proteins to be more stable through optimization of local structural entropy. The redesigned proteins display significant increases in their thermal stabilities while retaining catalytic activity, and demonstrate a broadly applicable method.