1rpf
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THE STRUCTURES OF RNASE COMPLEXED WITH 3'-CMP AND D(CPA): ACTIVE SITE CONFORMATION AND CONSERVED WATER MOLECULES
OverviewOverview
The interactions of RNase A with cytidine 3'-monophosphate (3'-CMP) and, deoxycytidyl-3',5'-deoxyadenosine (d(CpA)) were analyzed by X-ray, crystallography. The 3'-CMP complex and the native structure were, determined from trigonal crystals, and the d(CpA) complex from monoclinic, crystals. The differences between the overall structures are concentrated, in loop regions and are relatively small. The protein-inhibitor contacts, are interpreted in terms of the catalytic mechanism. The general base His, 12 interacts with the 2' oxygen, as does the electrostatic catalyst Lys, 41. The general acid His 119 has 2 conformations (A and B) in the native, structure and is found in, respectively, the A and the B conformation in, the d(CpA) and the 3'-CMP complex. From the present structures and from a, comparison with RNase T1, we propose that His 119 is active in the A, conformation. The structure of the d(CpA) complex permits a detailed, analysis of the downstream binding site, which includes His 119 and Asn, 71. The comparison of the present RNase A structures with an inhibitor, complex of RNase T1 shows that there are important similarities in the, active sites of these 2 enzymes, despite the absence of any sequence, homology. The water molecules were analyzed in order to identify conserved, water sites. Seventeen water sites were found to be conserved in RNase A, structures from 5 different space groups. It is proposed that 7 of those, water molecules play a role in the binding of the N-terminal helix to the, rest of the protein and in the stabilization of the active site.
About this StructureAbout this Structure
1RPF is a Single protein structure of sequence from Bos taurus with C3P as ligand. Active as Pancreatic ribonuclease, with EC number 3.1.27.5 Full crystallographic information is available from OCA.
ReferenceReference
The structures of RNase A complexed with 3'-CMP and d(CpA): active site conformation and conserved water molecules., Zegers I, Maes D, Dao-Thi MH, Poortmans F, Palmer R, Wyns L, Protein Sci. 1994 Dec;3(12):2322-39. PMID:7756988
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