Open AccesspH‐tuneable binding of 2′‐phospho‐ADP‐ribose to ketopantoate reductase: a structural and calorimetric study
Author(s) -
Ciulli Alessio,
Lobley Carina M. C.,
Tuck Kellie L.,
Smith Alison G.,
Blundell Tom L.,
Abell Chris
Publication year - 2007
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s0907444906044465
Subject(s) - isothermal titration calorimetry , nicotinamide , stereochemistry , chemistry , enzyme , protonation , nad+ kinase , ring (chemistry) , reductase , binding site , ligand (biochemistry) , active site , crystallography , biochemistry , organic chemistry , receptor , ion
The crystal structure of Escherichia coli ketopantoate reductase in complex with 2′‐monophosphoadenosine 5′‐diphosphoribose, a fragment of NADP + that lacks the nicotinamide ring, is reported. The ligand is bound at the enzyme active site in the opposite orientation to that observed for NADP + , with the adenine ring occupying the lipophilic nicotinamide pocket. Isothermal titration calorimetry with R31A and N98A mutants of the enzyme is used to show that the unusual `reversed binding mode' observed in the crystal is triggered by changes in the protonation of binding groups at low pH. This research has important implications for fragment‐based approaches to drug design, namely that the crystallization conditions and the chemical modification of ligands can have unexpected effects on the binding modes.