This old version of Proteopedia is provided for student assignments while the new version is undergoing repairs. Content and edits done in this old version of Proteopedia after March 1, 2026 will eventually be lost when it is retired in about June of 2026.
Apply for new accounts at the new Proteopedia. Your logins will work in both the old and new versions.
1low
From Proteopedia
X-ray structure of the H40A mutant of Ribonuclease T1 complexed with 3'-guanosine monophosphate
Overview
Ribonucleases (RNases) catalyze the cleavage of the phosphodiester bond in RNA up to 10(15)-fold, as compared with the uncatalyzed reaction. High resolution crystal structures of these enzymes in complex with 3'-mononucleotide substrates demonstrate the accommodation of the nucleophilic 2'-OH group in a binding pocket comprising the catalytic base (glutamate or histidine) and a charged hydrogen bond donor (lysine or histidine). Ab initio quantum chemical calculations performed on such Michaelis complexes of the mammalian RNase A (EC ) and the microbial RNase T(1) (EC ) show negative charge build up on the 2'-oxygen upon substrate binding. The increased nucleophilicity results from stronger hydrogen bonding to the catalytic base, which is mediated by a hydrogen bond from the charged donor. This hitherto unrecognized catalytic dyad in ribonucleases constitutes a general mechanism for nucleophile activation in both enzymic and RNA-catalyzed phosphoryl transfer reactions.
About this Structure
1LOW is a Single protein structure of sequence from Aspergillus oryzae. Full crystallographic information is available from OCA.
Reference
A nucleophile activation dyad in ribonucleases. A combined X-ray crystallographic/ab initio quantum chemical study., Mignon P, Steyaert J, Loris R, Geerlings P, Loverix S, J Biol Chem. 2002 Sep 27;277(39):36770-4. Epub 2002 Jul 16. PMID:12122018 Page seeded by OCA on Sat May 3 00:07:52 2008
