title: Determination of the NMR structure of Gln25-ribonuclease T1.
abstract: Ribonuclease (RNase) T1 is a guanyloribonuclease, having two isozymes in nature, Gln25- and Lys25-RNase T1. Between these two isozymes, there is no difference in catalytic activity and three-dimensional structure; however, Lys25-RNase T1 is slightly more stable than Gln25-RNase T1. Recently, it has been suggested that the existence of a salt bridge between Lys25 and Asp29/Glu31 in Lys25-RNase T1 contributes to the stability. To elucidate the effects of the replacement of Lys25 with a Gln on the conformation and microenvironments of RNase T1 in detail, the three-dimensional solution structure of Gln25-RNase T1 was determined by simulated-annealing calculations. As a result, the topology of the overall folding was shown to be very similar to that of the Lys25-isozyme except for some differences. In particular, there were two differences in the property of torsion angles of the two disulfide bonds and the conformations of the residues 11-13, 63-66, and 92-93. With regard to the residues 11-13, the lack of the above-mentioned salt bridge in Gln25-RNase T1 was thought to induce the conformational difference of this segment as compared with the Lys25-isozyme. Furthermore, it was proposed that the perturbation of this segment might transfer to the residues 92-93 via the two disulfide bonds.
authors.affiliation: Department of Biological Sciences, Faculty of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan.
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Hatano
authors.forename: Masaki
authors.initials: M
authors.lastname: Kojima
authors.forename: Ei-ichiro
authors.initials: E
authors.lastname: Suzuki
authors.forename: Masaru
authors.initials: M
authors.lastname: Tanokura
authors.forename: Kenji
authors.initials: K
authors.lastname: Takahashi
mesh_terms: D001665:Binding Sites; D002384:Catalysis; D004220:Disulfides / Q000737:chemistry; D005971:Glutamates / Q000737:chemistry; D005998:Glycine / Q000737:chemistry*; D006639:Histidine / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008239:Lysine / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D011487:Protein Conformation; D006163:Ribonuclease T1 / Q000737:chemistry*; D013329:Structure-Activity Relationship
chemical_list: D004220:Disulfides; D005971:Glutamates; D006639:Histidine; D006163:Ribonuclease T1; D008239:Lysine; D005998:Glycine