PDBsum entry 3eng

Glycosyl hydrolase

PDB id

3eng

Contents

			Protein chain

					213 a.a.

			Ligands

					BGC-BGC

			Waters ×145

References listed in PDB file

Key reference

Title

Structure determination and refinement of the humicola insolens endoglucanase V at 1.5 a resolution.

Authors

G.J.Davies, G.Dodson, M.H.Moore, S.P.Tolley, Z.Dauter, K.S.Wilson, G.Rasmussen, M.Schülein.

Ref.

Acta Crystallogr D Biol Crystallogr, 1996, 52, 7. [DOI no: 10.1107/S0907444995009280]

PubMed id

15299721

Abstract

The structure of the catalytic core of the endoglucanase V (EGV) from Humicola insolens has been determined by the method of multiple isomorphous replacement at 1.5 A resolution. The final model, refined with X-PLOR and PROLSQ, has a crystallographic R factor of 0.163 (R(free) = 0.240) with deviations from stereochemical target values of 0.012 A and 0.037 degrees for bonds and angles, respectively. The model was further refined with SHELXL, including anisotropic modelling of the protein-atom temperature factors, to give a final model with an R factor of 0.105 and an R(free) of 0.154. The initial isomorphous replacement electron-density map was poor and uninterpretable but was improved by the use of synchrotron data collected at a wavelength chosen so as to optimize the f" contribution of the anomalous scattering from the heavy atoms. The structure of H. insolens EGV consists of a six-stranded beta-barrel domain, similar to that found in a family of plant defence proteins, linked by a number of disulfide-bonded loop regions. A long open groove runs across the surface of the enzyme either side of which lie the catalytic aspartate residues. The 9 A separation of the catalytic carboxylate groups is consistent with the observation that EGV catalyzes the hydrolysis of the cellulose, beta(1-->4) links with inversion of configuration at the anomeric C1 atom. This structure is the first representative from the glycosyl hydrolase family 45.



	Figure 1. Fig. 1. Sections of the electron- density maps of EGV corre- sponding to residues 90-94. The three maps shown are a) MIR map (convntional source), (b) MIR map (optimized A) and (c) the 1.5 A 2Fo-Fc map. The two MIR maps are contoured at a level of l cr and the 2Fo- F,. map at a level of 04 e A -3.		Figure 10. Fig. 10. 2Fo- Fc electron density, contoured at 0.44 e A. -3, for the catalytic centr of EGV. The proposed proton donor, Asp 121, and the catalytic base, Aspl0, are labelled. Aspl21 is involved in a hydrogen-bonding network involving residues Thr6 and His119, as indicated.