Abstract
The crystal structure of ribonuclease A with bound thymidylic acid tetramer is reported at 2.5-A resolution. The diffusion of the tetramer into native orthorhombic crystals of the ribonuclease allows for the formation of a structurally stable complex where the single-stranded nucleic acid enters and leaves the enzyme's catalytic region in a persistent 5'-3' direction. The binding of the tetramer to the enzyme's surface is facilitated and mediated by electrostatic interactions between basic protein residues and nucleotide phosphates. Two pyrimidine nucleotides are bound to the enzyme's active site in a manner similar to that observed for other complexes between ribonuclease A and nucleic acid oligomers.
Highlights
From the $Divisionof Biomedical Sciences, Lawrence Livermore National Laboratory, Universityof California, Livermore, California 94550 and the TDepartment of Biochemistry, University of California, Riverside, California92521
The diffusion of the tetramer into native orthorhombic crystals of the ribonuclease allows for the formation of a structurally stable complex where the single-stranded nucleic acid enters and leaves the enzyme’s catalytic region in a persistent 5’-3’ direction
Two pyrimidine nucleotides are bound to the enzyme’s active site in a manner similar to that observed for other complexes between ribonuclease A and nucleic acid oligomers
Summary
THEJOURNALOF BIOLOGICALCHEMISTRY 0 1992 by The American Society for Biochemistry and Molecular Biology, Inc. Structure Solutions and Refinements-A model for the RNase A structure, based on a combination of x-ray diffraction and neutron diffraction data (Wlodawer and Hendrickson, 1982; Wlodawer and Sjolin, 1983) from crystalsnot grown in the presence of p-octyl glucoside, had previouslybeen used as a molecular replacement model t o position the RNase A molecule in the P212121unit cells of native protein crystals with the typical prismatic habit seen of RNase A crystals grown inPEG 4000 (Brayer and McPherson, 1982) This model, with its positioning in the orthorhombic unit cell, was initially used to solve the structure of the enzyme using reflection data from native crystals of the present study. Rotation function and translation function searches under X-PLOR (Brunger, 1990),using the refined structure for RNase A
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