Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026837 (muscle rigidity)
 1,077 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Backbone conformational fluctuations on multiple time scales in a cysteine-free Thermus thermophilus ribonuclease HI mutant (ttRNH(*)) are quantified using (15)N nuclear magnetic spin relaxation. Laboratory-frame relaxation data acquired at 310 K and at static magnetic field strengths of 11.7, 14.1 and 18.8 T are analysed using reduced spectral density mapping and model-free approaches. Chemical exchange line broadening is characterized using Hahn-echo transverse and multiple quantum relaxation data acquired over a temperature range of 290-320 K and at a static magnetic field strength of 14.1 T. Results for ttRNH(*) are compared to previously published data for a mesophilic homologue, Escherichia coli ribonuclease HI (ecRNH). Intramolecular conformational fluctuations on the picosecond-to-nanosecond time scale generally are similar for ttRNH(*) and ecRNH. beta-Strands 3 and 5 and the glycine-rich region are more rigid while the substrate-binding handle region and C-terminal tail are more flexible in ttRNH(*) than in ecRNH. Rigidity in the two beta-strands and the glycine-rich region, located along the periphery of the central beta-sheet, may be associated with the increased thermodynamic stability of the thermophilic enzyme. Chemical exchange line broadening, reflecting microsecond-to-millisecond time scale conformational changes, is more pronounced in ttRNH(*) than in ecRNH, particularly for residues in the handle and surrounding the catalytic site. The temperature dependence of chemical exchange show an increase of approximately 15 kJ/mol in the apparent activation energies for ttRNH(*) residues in the handle compared to ecRNH. Increased activation barriers, coupled with motion between alpha-helices B and C not present in ecRNH, may be associated with the reduced catalytic activity of the thermophilic enzyme at 310 K.
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PMID:Multiple time scale backbone dynamics of homologous thermophilic and mesophilic ribonuclease HI enzymes. 1516 55