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192 a.a.
_ZN
Key reference
DOI no: 10.1074/jbc.M513066200 J Biol Chem 281:10968-10975 (2006) PubMed id: 16431911
Structure and activity of two metal ion-dependent acetylxylan esterases involved in plant cell wall degradation reveals a close similarity to peptidoglycan deacetylases. E.J.Taylor, T.M.Gloster, J.P.Turkenburg, F.Vincent, A.M.Brzozowski, C.Dupont, F.Shareck, M.S.Centeno, J.A.Prates, V.Puchart, L.M.Ferreira, C.M.Fontes, P.Biely, G.J.Davies. ABSTRACT
The enzymatic degradation of plant cell wall xylan requires the concerted action of a diverse enzymatic syndicate. Among these enzymes are xylan esterases, which hydrolyze the O-acetyl substituents, primarily at the O-2 position of the xylan backbone. All acetylxylan esterase structures described previously display a alpha/beta hydrolase fold with a "Ser-His-Asp" catalytic triad. Here we report the structures of two distinct acetylxylan esterases, those from Streptomyces lividans and Clostridium thermocellum, in native and complex forms, with x-ray data to between 1.6 and 1.0 A resolution. We show, using a novel linked assay system with PNP-2-O-acetylxyloside and a beta-xylosidase, that the enzymes are sugar-specific and metal ion-dependent and possess a single metal center with a chemical preference for Co2+. Asp and His side chains complete the catalytic machinery. Different metal ion preferences for the two enzymes may reflect the surprising diversity with which the metal ion coordinates residues and ligands in the active center environment of the S. lividans and C. thermocellum enzymes. These "CE4" esterases involved in plant cell wall degradation are shown to be closely related to the de-N-acetylases involved in chitin and peptidoglycan degradation (Blair, D. E., Schuettelkopf, A. W., MacRae, J. I., and Aalten, D. M. (2005) Proc. Natl. Acad. Sci. U. S. A., 102, 15429-15434), which form the NodB deacetylase "superfamily."
Selected figure(s)
Figure 4.
FIGURE 4. Comparison of the S. lividans acetylxylan esterase, SlCE4, and the peptidoglycan deacetylase from S. pneumonia. A, ribbon representation of SlCE4 (green) overlapped with the peptidoglycan de-N-acetylase from S. pneumonia (purple). Active site residues and acetate molecules (gray) are shown in ball-and-stick representation and Zn^2+ ions as spheres. B, divergent stereo ball-and-stick representation of SlCE4 active site residues (green) overlapped with those from the peptidoglycan de-N-acetylase from S. pneumonia (purple and labeled); the acetate molecules are shown in green/gray. Zn^2+ ions (cyan) and water molecules are shown as spheres. Figures were made using MOLSCRIPT (44, 45) and rendered using RASTER3D (46).Figure 7.
FIGURE 7. Active site interactions and catalysis in family CE4 acetylxylan esterases. Schematic diagram of the metal ion coordination of the S. lividans family CE4 esterase (acetate shown in red)(A) and the C. thermocellum CE4 esterase (B) and a putative reaction mechanism (C) based upon classical Zn^2+ hydrolase chemistry and the work of van Aalten and colleagues (19) on the streptococcal peptidoglycan deacetylases. The divalent metal plays the role of Lewis acid, with Asp and His residues playing the roles of catalytic base (activating the nucleophilic water) and acid (aiding sugar departure).The above figures are reprinted by permission from the ASBMB: J Biol Chem (2006, 281, 10968-10975) copyright 2006. Figures were selected by an automated process.
Literature references that cite this PDB file's key reference
PubMed id Reference
18978064 D.M.Deng, J.E.Urch, J.M.ten Cate, V.A.Rao, D.M.van Aalten, and W.Crielaard (2009).
Streptococcus mutans SMU.623c codes for a functional, metal-dependent polysaccharide deacetylase that modulates interactions with salivary agglutinin.J Bacteriol, 191, 394-402.
PDB code: 2w3z
19472335 J.E.Urch, R.Hurtado-Guerrero, D.Brosson, Z.Liu, V.G.Eijsink, C.Texier, and D.M.van Aalten (2009).
Structural and functional characterization of a putative polysaccharide deacetylase of the human parasite Encephalitozoon cuniculi.Protein Sci, 18, 1197-1209.
18070068 W.Vollmer (2008).
Structural variation in the glycan strands of bacterial peptidoglycan.FEMS Microbiol Rev, 32, 287-306.
18978092 X.L.Li, C.D.Skory, M.A.Cotta, V.Puchart, and P.Biely (2008).
Novel family of carbohydrate esterases, based on identification of the Hypocrea jecorina acetyl esterase gene.Appl Environ Microbiol, 74, 7482-7489.
17063474 L.Oberbarnscheidt, E.J.Taylor, G.J.Davies, and T.M.Gloster (2007).
Structure of a carbohydrate esterase from Bacillus anthracis.Proteins, 66, 250-252.
PDB code: 2j13
17623028 S.Ding, J.Cao, R.Zhou, and F.Zheng (2007).
Molecular cloning, and characterization of a modular acetyl xylan esterase from the edible straw mushroom Volvariella volvacea.FEMS Microbiol Lett, 274, 304-310. The most recent references are shown first. Citation data come partly from CiteXplore and partly from an automated harvesting procedure. Note that this is likely to be only a partial list as not all journals are covered by either method. However, we are continually building up the citation data so more and more references will be included with time. Where a reference describes a PDB structure, the PDB code is shown on the right.
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