1rgc
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(New page: 200px<br /><applet load="1rgc" size="450" color="white" frame="true" align="right" spinBox="true" caption="1rgc, resolution 2.0Å" /> '''THE COMPLEX BETWEEN R...)
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THE COMPLEX BETWEEN RIBONUCLEASE T1 AND 3'-GUANYLIC ACID SUGGESTS GEOMETRY OF ENZYMATIC REACTION PATH. AN X-RAY STUDY
Overview
The crystal structure of the complex between ribonuclease T1 and 3'GMP, suggests that (a) a substrate GpN is bound to the active site of, ribonuclease T1 in a conformation that actively supports the catalytic, process, (b) the reaction occurs in an in-line process, (c) His40 N, epsilon H+ activates O2'-H, (d) Glu58 carboxylate acts as base and His92 N, epsilon H+ as acid in a general acid-base catalysis. The crystals have the, monoclinic space group P2(1), a = 4.968 nm, b = 4.833 nm, c = 4.048 nm, beta = 90.62 degrees with two molecules in the asymmetric unit. The, structure was determined by molecular replacement and refined to R = 15.3%, with 11,338 data > or = 1 sigma (Fo) in the resolution range 1.0-0.2 nm;, this includes 180 water molecules and two Ca2+. The structure of, ribonuclease T1 is as previously observed. 3'GMP is bound in syn, conformation; guanine is located in the specific recognition site, the, ribose adopts C4'-exo puckering, the ribose phosphate is extended with, torsion angle epsilon in trans. The O2'-H group is activated by accepting, and donating hydrogen bonds from His40 N epsilon H+ and to Glu58 O epsilon, 1; the phosphate is hydrogen bonded to Glu58 O epsilon 2H, Arg77 N epsilon, H+ and N eta 2H+, Tyr38 O eta H, His92 N eta H+. The conformation of, ribose phosphate is such that O2' is at a distance of 0.31 nm from, phosphorus, and opposite the P-OP3 bond which accepts a hydrogen bond from, His92 N epsilon H+; we infer from a model building study that this bond is, equivalent to the scissile P-O5' in a substrate GpN.
About this Structure
1RGC is a Single protein structure of sequence from Aspergillus oryzae with CA and 3GP as ligands. Active as Ribonuclease T(1), with EC number 3.1.27.3 Full crystallographic information is available from OCA.
Reference
The complex between ribonuclease T1 and 3'GMP suggests geometry of enzymic reaction path. An X-ray study., Heydenreich A, Koellner G, Choe HW, Cordes F, Kisker C, Schindelin H, Adamiak R, Hahn U, Saenger W, Eur J Biochem. 1993 Dec 15;218(3):1005-12. PMID:8281918
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