Final Report: Structural studies of archatelthermophilic adenylate kinase, September 15, 1996 - September 14, 1998

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Through this DOE sponsored program Konisky has studied the evolution and molecular biology of microbes that live in extreme environments. The emphasis of this work has been the determination of the structural features of thermophilic enzymes that allow them to function optimally at near 100%. The laboratory has focused on a comparative study of adenylate kinase (ADK), an enzyme that functions to interconvert adenine nucleotides. Because of the close phylogenetic relatedness of members of the methanococci, differences in the structure of their ADKs will be dominated by structural features that reflect contributions to their optimal temperature for activity, rather than ... continued below

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2 p.

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Konisky, Jordan September 14, 1998.

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Description

Through this DOE sponsored program Konisky has studied the evolution and molecular biology of microbes that live in extreme environments. The emphasis of this work has been the determination of the structural features of thermophilic enzymes that allow them to function optimally at near 100%. The laboratory has focused on a comparative study of adenylate kinase (ADK), an enzyme that functions to interconvert adenine nucleotides. Because of the close phylogenetic relatedness of members of the methanococci, differences in the structure of their ADKs will be dominated by structural features that reflect contributions to their optimal temperature for activity, rather than differences due to phylogenetic divergence. The authors have cloned, sequenced and modeled the secondary structure for several methanococcal ADKs. using molecular modeling threading approaches that are based on the solved structure for the porcine ADK, they have also proposed a general low resolution three dimensional structure for each of the methanococcal enzymes. These analyzes have allowed them to propose structural features that confer hyperthermoactivity to those enzymes functioning in the hyperthermophilic members of the Methanococci. Using protein engineering methodologies, they have tested their hypotheses by examining the effects of selective structural changes on thermoactivity. Despite possessing between 68--83% sequence identity, the methanococcal AKs had significantly different stability against thermal denaturation, with melting points ranging from 69--103 C. The construction of several chimerical AKs by linking regions of the MVO and MJA AKs demonstrated the importance of cooperative interactions between amino- and carboxyl-terminal regions in influencing thermostability. Addition of MJA terminal fragments to the MVO AK increased thermal stability approximately 20 C while maintaining 88% of the mesophilic sequence. Further analysis using structural models suggested that hydrophobic interactions are largely responsible for determining the thermostability of the methanococcal AKs. Construction of chimerical enzyme also demonstrated a distinct separation between thermostability and enzymatic temperature optima, suggesting that overall protein flexibility and stability are not dependently linked. Sequence comparisons and model buildings of highly related archaeal adenylate kinases has allowed the prediction of interactions responsible for the large temperature variation in temperatures for of optimal catalytic activity and temperature stability. The tertiary structure for these ADK have been predicted by using homology modeling to further investigate the potential of specific interactions on thermal stability and activity.

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2 p.

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OSTI as DE00756672

Medium: P; Size: 2 pages

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  • Other Information: PBD: 14 Sep 1998

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  • Report No.: NONE
  • Grant Number: FG03-96ER20241
  • DOI: 10.2172/756672 | External Link
  • Office of Scientific & Technical Information Report Number: 756672
  • Archival Resource Key: ark:/67531/metadc701932

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  • September 14, 1998

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  • Sept. 12, 2015, 6:31 a.m.

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  • April 10, 2017, 3 p.m.

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Konisky, Jordan. Final Report: Structural studies of archatelthermophilic adenylate kinase, September 15, 1996 - September 14, 1998, report, September 14, 1998; United States. (digital.library.unt.edu/ark:/67531/metadc701932/: accessed September 20, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.