Reference "Crystal structure of barley 1,3-1,4-beta-glucanase at 2.0-A resolution and comparison with Bacillus 1,3-1,4-beta-glucanase"

Reference ID

8646

Title

Crystal structure of barley 1,3-1,4-beta-glucanase at 2.0-A resolution and comparison with Bacillus 1,3-1,4-beta-glucanase

Source

The Journal of biological chemistry, 1998, vol. 273, pp. 3438-3446

Authors (3)

Muller-J-J	Thomsen-K-K
Heinemann-U

Abstract

Both plants and bacteria produce enzymes capable of degrading the mixed-linked
beta-glucan of the endosperm cell walls of cereal grains. The enzymes share the
specificity for beta-1,4 glycosyl bonds of O-3-substituted glucose units in
linear polysaccharides and a similar cleavage mechanism but are unrelated in
sequence and tertiary structure. The three-dimensional structure of the 1,3-1,
4-beta-glucanase isoenzyme EII from barley was determined from monoclinic
crystals at a resolution of 2.0 A. The protein is folded into a betaalpha8
barrel structure as has been shown previously (Varghese, J. N., Garrett, T. P.
J., Colman, P. M., Chen, L., Hoj, P. B., and Fincher, G. B. (1994) Proc. Natl.
Acad. Sci. U.S.A. 91, 2785-2789) by diffraction analysis at lower resolution of
tetragonal crystals. It contains one N-glycosylation site which is described in
detail with the sugar moieties attached to residue Asn190. The geometry and
hydration of the barley 1,3-1,4-beta-glucanase is analyzed; a model beta-glucan
fragment is placed into the binding site by molecular dynamics simulation, and
the beta-glucan binding grooves of the plant and bacterial enzymes are compared.
Their active sites are shown to have a small number of common features in
generally dissimilar geometries that serve to explain both the identical
substrate specificity and the observed differences in inhibitor binding.