Ribonucleases A and T1 Comparable Mechanisms of RNA Cleavage with Different Active Site Geometries
There are a variety of enzymes which cleave the phosphodiester link in ribo- and deoxyribonucleic acids. They exhibit different catalytic activities, different mechanisms of cleavage, and different three-dimensional structures. The best known examples are DNase I which acts upon single and double stranded DNA , staphylococcal nuclease which cleaves P-0 bonds in RNA and DNA single strands2 , and the two RNases A and T1 which cut at the 3′-end of pyrimidine and guanosine nucleotides respectively3-5 . Although the two RNases have different molecular topology, the mechanism of hydrolysis is similar and suggestive of a comparable active site geometry. Since high resolution crystal structures are available (1.5Å for RNase A and 2.oÅ for RNase T1)3-5, a study of the arrangement of the functional amino acids in the1 active sites of the two enzymes is of interest.
KeywordsActive Site Residue Pancreatic Ribonuclease Staphylococcal Nuclease Functional Amino Acid Guanosine Nucleotide
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- 3.A. Wlodawer, Structure of bovine pancreatic ribonuclease by X-ray and neutron diffraction, pp. 393–439, in “Biological Macromolecules and Assemblies, Vol. II. Nucleic Acids and Interactive Proteins”, F.A. Jurnak and A. McPherson, eds., John Wiley & Sons, New York (1985) .Google Scholar
- 5.R. Arni, Ph.D. Thesis Freie Universität Berlin, to be submitted (1986).Google Scholar
- 9.K. Takahashi, The structure and function of ribonuclease T1 . XXI. Modification of histidine residues in ribonuclease T1 with iodoacetamide, J. Biochem. (Tokyo) 80:1267–1275 (1976).Google Scholar