1ccu

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spinqualitylabelsall models 1ccu, resolution 2.25Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

STRUCTURE-ASSISTED REDESIGN OF A PROTEIN-ZINC BINDING SITE WITH FEMTOMOLAR AFFINITY

Contents 1 Overview 2 Disease 3 About this Structure 4 Reference

Overview

We have inserted a fourth protein ligand into the zinc coordination, polyhedron of carbonic anhydrase II (CAII) that increases metal affinity, 200-fold (Kd = 20 fM). The three-dimensional structures of, threonine-199-->aspartate (T199D) and threonine-199-->glutamate (T199E), CAIIs, determined by x-ray crystallographic methods to resolutions of 2.35, Angstrum and 2.2 Angstrum, respectively, reveal a tetrahedral, metal-binding site consisting of H94, H96, H119, and the engineered, carboxylate side chain, which displaces zinc-bound hydroxide. Although the, stereochemistry of neither engineered carboxylate-zinc interaction is, comparable to that found in naturally occurring protein zinc-binding, sites, protein-zinc affinity is enhanced in T199E CAII demonstrating that, ligand-metal separation is a significant determinant of carboxylate-zinc, affinity. In contrast, the three-dimensional structure of, threonine-199-->histidine (T199H) CAII, determined to 2.25-Angstrum, resolution, indicates that the engineered imidazole side chain rotates, away from the metal and does not coordinate to zinc; this results in a, weaker zinc-binding site. All three of these substitutions nearly, obliterate CO2 hydrase activity, consistent with the role of zinc-bound, hydroxide as catalytic nucleophile. The engineering of an additional, protein ligand represents a general approach for increasing protein-metal, affinity if the side chain can adopt a reasonable conformation and achieve, inner-sphere zinc coordination. Moreover, this structure-assisted design, approach may be effective in the development of high-sensitivity metal ion, biosensors.

Disease

Known disease associated with this structure: Osteopetrosis, autosomal recessive 3, with renal tubular acidosis OMIM:[611492]

About this Structure

1CCU is a Single protein structure of sequence from Homo sapiens with and as ligands. Active as Carbonate dehydratase, with EC number 4.2.1.1 Full crystallographic information is available from OCA.

Reference

Structure-assisted redesign of a protein-zinc-binding site with femtomolar affinity., Ippolito JA, Baird TT Jr, McGee SA, Christianson DW, Fierke CA, Proc Natl Acad Sci U S A. 1995 May 23;92(11):5017-21. PMID:7761440

Page seeded by OCA on Fri Feb 15 15:35:14 2008