Determination and restrained least-squares refinement of the structures of ribonuclease Sa and its complex with 3'-guanylic acid at 1.8 Å resolution

Autor:	J. Sevcik, E. J. Dodson, G. G. Dodson
Rok vydání:	1991
Předmět:	biology RNase P Resolution (electron density) Substrate (chemistry) Guanosine Active site General Medicine Crystal structure General Biochemistry Genetics and Molecular Biology chemistry.chemical_compound Crystallography chemistry X-ray crystallography biology.protein Molecule
Zdroj:	Acta Crystallographica Section B Structural Science. 47:240-253
ISSN:	0108-7681
DOI:	10.1107/s0108768190009569
Popis:	The crystal structures of ribonuclease from Streptomyces aureofaciens (RNase Sa) and its complex with 3'-guanylic acid (guanosine 3'-monophosphate, 3'-GMP) have been determined by the method of isomorphous replacement. The atomic parameters have been refined by restrained least-squares minimization using data in the resolution range 10.0-1-8 A. All protein atoms and more than 230 water atoms in the two crystal structures have been refined to crystallographic R factors of 0.172 and 0.175 respectively. The estimated r.m.s, error in the atomic positions ranges from 0.2 A for well-defined atoms to about 0.5 A for more poorly defined atoms. There are two enzyme molecules in the asymmetric unit, built independently, and referred to as molecules A and B. The value of the average B factor for protein atoms in both structures is about 19 A 2 and for water molecules about 35 A2. Electron density for the substrate analogue 3'-GMP was found only at the active site of molecule A. The density was very clear and the positions of all 3'-GMP atoms were refined with precision comparable to that of the protein.
Databáze:	OpenAIRE
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