title: Structural properties of the histidine-containing loop in HIV-1 RNase H.
abstract: The isolated HIV-1 RNase H domain is inactive. This inactivity has been linked to the lack of structure in the C-terminus of the isolated domain. Thermodynamic stability experiments on the RNase H domain as well as a deletion mutant lacking the C-terminal helix have implied that this region is structured. His539 residing in a loop preceding the C-terminal helix was studied by NMR to determine the stability and conformational properties of this region. The stability of the structural environment of His539 matches that of the entire RNase H domain. Furthermore, His539 is locked into a defined tautometric state in the folded protein and its pK(a) is shifted compared to a freely accessible His, suggesting that this region is structured. The data support the view that the overall dynamics rather than the lack of structure in a small portion of the protein render activity of the isolated HIV-1 RNase H.
authors.affiliation: Department of Molecular and Cell Biology, 229 Stanley Hall, University of California, Berkeley, CA 94720, USA. gunther.kern@astrazeneca.com
authors.forename: Gunther
authors.initials: G
authors.lastname: Kern
authors.forename: Jeff
authors.initials: J
authors.lastname: Pelton
authors.forename: Susan
authors.initials: S
authors.lastname: Marqusee
authors.forename: Dorothee
authors.initials: D
authors.lastname: Kern
mesh_terms: D015497:HIV-1 / Q000201:enzymology*; D006639:Histidine / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D011489:Protein Denaturation / Q000187:drug effects; D016914:Ribonuclease H / Q000737:chemistry*; D013329:Structure-Activity Relationship; D014508:Urea / Q000494:pharmacology
chemical_list: D006639:Histidine; D014508:Urea; D016914:Ribonuclease H