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Not different, Just Better: The Adaptive Evolution of an Enzyme

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Technical Report,01 Oct 2011,30 Sep 2015

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University of Canterbury Christchurch New Zealand

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We know much about the consequences of adaptation, but little of the underlying molecular causes. Our program combined biochemical, biophysical and evolutionary experiments to rigorously examine the molecular and biochemical basis of adaptation, mediated by changes in pyruvate kinase found in Richard Lenskis E. coli long-term evolution experiment. We have demonstrated, for the first time, that all the pykF mutations found in the E. coli long-term evolution experiment confer a significant adaptive fitness advantage to the bacterium. Moreover, we have shown that the mutations are likely to have a similar proximal basis of the benefit they confer a shorter lag phase of the growth cycle. Not only are adaptive mutations often parallel at the physiological and genetic level, they are also parallel at the molecular level. The key finding from our program is that while the adaptive mutations in pyruvate kinase significantly alter the catalytic and allosteric function of the enzyme, they do not change the overall structure of the proteins or their thermal stability. Instead, we have demonstratedusing cutting edge deuterium exchange studies and molecular dynamic simulations that the dynamics of key loops surrounding the active site are altered, which explain the changes in catalytic function.

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