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PDBsum entry 5rnt
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Hydrolase(endoribonuclease)
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PDB id
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5rnt
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References listed in PDB file
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Key reference
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Title
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X-Ray analysis of cubic crystals of the complex formed between ribonuclease t1 and guanosine-3',5'-Bisphosphate.
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Authors
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A.Lenz,
U.Heinemann,
M.Maslowska,
W.Saenger.
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Ref.
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Acta Crystallogr B, 1991,
47,
521-527.
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PubMed id
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Abstract
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The complex formed between ribonuclease T1 (RNase T1) and
guanosine-3',5'-bisphosphate (3',5'-pGp) crystallizes in the cubic space group
I23 with alpha = 86.47 (4) A. X-ray data were collected on a four-circle
diffractometer to 3.2 A resolution and the structure was determined by
molecular-replacement methods [ULTIMA; Rabinovich & Shakked (1984). Acta
Cryst. A40, 195-200] based on the RNase T1 coordinates taken from the complex
with guanosine-2'-phosphate. Refinement converged at 16.6% for 1540 data with Fo
greater than 1 sigma (Fo) with acceptable stereochemistry. The RNase T1
conformation is comparable to that in other complexes which crystallize
preferentially in space group P2(1)2(1)2(1) except for side chains that interact
intermolecularly. The guanine of 3',5'-pGp is bound to the recognition site in
the same way as in other guanine-containing complexes except for its interaction
with Glu46. The side-chain carboxylate of this amino acid does not form hydrogen
bonds to N1H and N2H of guanine but is rotated so as to permit insertion of two
water molecules which replace its acceptor functions. In contrast to other
guanosine derivatives which are bound to RNase T1 in the syn form, 3',5'-pGp is
anti. This conformation positions the two phosphate groups 'outside' the
protein, with hydrogen-bonding contacts only to water molecules; the active site
is filled by water. The RNase T1-3',5'-pGp complex probably has biological
significance as it may represent the enzyme-product complex before dissociation.
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