HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) All Versions of this Article: ps.062398606v1 15/12/2697    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Butterwick, J. A. Articles by Palmer, A. G. Search for Related Content PubMed PubMed Citation Articles by Butterwick, J. A. Articles by Palmer, A. G., III Social Bookmarking                   What's this?

An inserted Gly residue fine tunes dynamics between mesophilic and thermophilic ribonucleases H

Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA

(RECEIVED June 13, 2006; FINAL REVISION September 12, 2006; ACCEPTED September 18, 2006)

Dynamic processes are inherent properties of proteins and are crucial for a wide range of biological functions. To address how changes in protein sequence and structure affect dynamic processes, a quantitative comparison of microsecond-to-microsecond time scale conformational changes, measured by solution NMR spectroscopy, within homologous mesophilic and thermophilic ribonuclease H (RNase H) enzymes is presented. Kinetic transitions between the observed major state (high population) and alternate (low population) conformational state(s) of the substrate-binding handle region in RNase H from the mesophile Escherichia coli (ecRNH) and thermophile Thermus thermophilus (ttRNH) occur with similar kinetic exchange rate constants, but the difference in stability between exchanging conformers is smaller in ttRNH compared to ecRNH. The altered thermodynamic equilibrium between kinetically exchanging conformers in the thermophile is recapitulated in ecRNH by the insertion of a Gly residue within a putative hinge between -helices B and C. This Gly insertion is conserved among thermophilic RNases H, and allows the formation of additional intrahelical hydrogen bonds. A Gly residue inserted between -helices B and C appears to relieve unfavorable interactions in the transition state and alternate conformer(s) and represents an important adaptation to adjust conformational changes within RNase H for activity at high temperatures.

Keywords: nuclear magnetic resonance; ribonuclease H; protein dynamics; thermal stability

Reprint requests to: Arthur G. Palmer III, Department of Biochemistry and Molecular Biophysics, Columbia University, 650 West 168 Street, Black Building 507, New York, NY 10032, USA; e-mail: agp6{at}columbia.edu; fax: (212) 305-6949.

Article published online ahead of print. Article and publication date are at http://www.proteinscience.org/cgi/doi/10.1110/ps.062398606.

CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?