Linked Life Data

11786017

Source:http://linkedlifedata.com/resource/pubmed/id/11786017

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
2002-1-11
pubmed:databankReference
pubmed:abstractText
The crystal structure of the ternary complex of hexameric purine nucleoside phosphorylase (PNP) from Escherichia coli with formycin A derivatives and phosphate or sulphate ions is determined at 2.0 A resolution. The hexamer is found as a trimer of unsymmetric dimers, which are formed by pairs of monomers with active sites in different conformations. The conformational difference stems from a flexible helix (H8: 214-236), which is continuous in one conformer, and segmented in the other. With the continuous helix, the entry into the active site pocket is wide open, and the ligands are bound only loosely ("open" or "loose binding" conformation). By segmentation of the helix (H8: 214-219 and H8': 223-236, separated by a gamma-turn), the entry into the active site is partially closed, the pocket is narrowed and the ligands are bound much more tightly ("closed" or "tight binding" conformation). Furthermore, the side-chain of Arg217 is carried by the moving helix into the active site. This residue, conserved in all homologous PNPs, plays an important role in the proposed catalytic mechanism. In this mechanism, substrate binding takes place in the open, and and the catalytic action occurs in the closed conformation. Catalytic action involves protonation of the purine base at position N7 by the side-chain of Asp204, which is initially in the acid form. The proton transfer is triggered by the Arg217 side-chain which is moved by the conformation change into hydrogen bond distance to Asp204. The mechanism explains the broad specificity of E. coli PNP, which allows 6-amino as well as 6-oxo-nucleosides as substrates. The observation of two kinds of binding sites is fully in line with solution experiments which independently observe strong and weak binding sites for phosphate as well as for the nucleoside inhibitor.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
0022-2836
pubmed:author
pubmed:copyrightInfo
Copyright 2002 Academic Press.
pubmed:issnType
Print
pubmed:day
18
pubmed:volume
315
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
351-71
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed-meshheading:11786017-Binding Sites, pubmed-meshheading:11786017-Catalysis, pubmed-meshheading:11786017-Crystallization, pubmed-meshheading:11786017-Crystallography, X-Ray, pubmed-meshheading:11786017-Dimerization, pubmed-meshheading:11786017-Escherichia coli, pubmed-meshheading:11786017-Fluorescence, pubmed-meshheading:11786017-Formycins, pubmed-meshheading:11786017-Guanosine, pubmed-meshheading:11786017-Hydrogen Bonding, pubmed-meshheading:11786017-Inosine, pubmed-meshheading:11786017-Kinetics, pubmed-meshheading:11786017-Models, Molecular, pubmed-meshheading:11786017-Nucleosides, pubmed-meshheading:11786017-Phosphates, pubmed-meshheading:11786017-Protein Structure, Quaternary, pubmed-meshheading:11786017-Purine-Nucleoside Phosphorylase, pubmed-meshheading:11786017-Structure-Activity Relationship, pubmed-meshheading:11786017-Sulfates, pubmed-meshheading:11786017-Titrimetry
pubmed:year
2002
pubmed:articleTitle
Open and closed conformation of the E. coli purine nucleoside phosphorylase active center and implications for the catalytic mechanism.
pubmed:affiliation
Freie Universität Berlin, Institut für Chemie-Kristallographie, Takustrasse 6, D-14195 Berlin, Germany. koellner@chemie.fu-berlin.de
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't