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Content Provider | World Health Organization (WHO)-Global Index Medicus |
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Author | Vallee, B. L. Riordan, J. F. Russo, N. Shapiro, R. Acharya, K. R. |
Description | Author Affiliation: Russo N ( Center for Biochemical and Biophysical Sciences and Medicine, Harvard Medical School, Boston, MA 02115.); |
Abstract | The crystal structure of human angiogenin (reported in the preceding paper in this issue) reveals that the site that corresponds to the pyrimidine binding site of RNase A is obstructed by Gln-117. Mutation of this residue to Ala and Gly is here found to increase activity 11- to 18-fold and 21- to 30-fold, respectively, toward dinucleotide, polynucleotide, and cyclic nucleotide substrates, but without changing specificity. The enhanced activity of Q117G toward CpA is due to a 5-fold decrease in Km and a 6-fold increase in kcat. Its Ki value for 2'-CMP is 5-fold lower than that of native angiogenin, whereas its Ki value for 5'-AMP is unchanged. It has been reported previously that mutating Asp-116 to Ala increases activity 15-fold. The double mutant D116A/Q117A is shown to be only slightly more active than each individual mutant. The present results demonstrate that Gln-117 impedes the ribonucleolytic activity of angiogenin, as predicted by x-ray crystallography. Moreover, they suggest that prior to or during catalysis angiogenin must undergo a conformational change to reorient the C-terminal segment that contains this residue, and that a similar reorganization is required for the mutants as well. This view is supported by molecular modeling of an angiogenin-uridine vanadate complex. These in vitro findings have implications for the angiogenic activity of angiogenin in vivo. |
ISSN | 00278424 |
e-ISSN | 10916490 |
Journal | Proceedings of the National Academy of Sciences of the United States of America |
Issue Number | 8 |
Volume Number | 91 |
Language | English |
Publisher | National Academy of Sciences |
Publisher Date | 1994-05-01 |
Publisher Place | United States |
Access Restriction | Open |
Subject Keyword | Proteins Chemistry Ribonuclease, Pancreatic Ribonucleases Binding Sites DNA Primers Glutamine Kinetics Models, Molecular Molecular Sequence Data Mutagenesis, Site-Directed Protein Structure, Tertiary Structure-Activity Relationship Substrate Specificity Research Support, Non-U.S. Gov't Multidisciplinary |
Content Type | Text |
Resource Type | Article |
Subject | Multidisciplinary |
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