Structural, Thermodynamic, and Functional Mechanisms of Adaptations WrbA and AdoMetDC Proteins in Extremophilic Organisms
Final rept. 1 Feb-15 Aug 2007
PENNSYLVANIA STATE UNIV COLL OF MEDICINE HERSHEY
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One of the open questions of structural biology is the understanding of the mechanisms by which enzymes adapt to extreme temperatures, both high thermophilic and low psychrophilic. A model protein used in this study, S-adenosyl-methionine decarboxylase AdoMetDC, is a key enzyme in the polyamine biosynthesis and thus its activity should be strongly dependent on the environmental variables such as temperature. To date we completed the experimental characterization of the thermophilic AdoMtDC from Termatoga maritima. The processing of TmAdoMetDC that leads to catalytically active enzyme is undetectable at room temperature, but increases with the increase in temperature k0.41-0.08 hexp -1exp -1 at 65C. The binding constant for MMTA, an inhibitor that mimics natural substrate S adenosyl-methionine, was found to be on the order of 1 micron. A paper that summarizes these results is currently in preparation. The genes for AdoMtDC from five different bacteria have been cloned Leptospira interrogans psychiophile, Exiguobacterium sibiricum, psychrophile, Petrotoga mobilis thermophilic anaerobe, and Oceanobacillus iheyensis halophilic. All these proteins have been expressed and purified, and structural crystallization for x-ray analysis, biophysical e.g. stability, oligomerization and biochemical activity profile as a function of temperature and salt concentrations, activation energy experiments are currently in progress.
- Genetic Engineering and Molecular Biology