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304 a.a.
Key reference
DOI no: 10.1016/S0014-5793(02)02954-X FEBS Lett 523:103-108 (2002) PubMed id: 12123813
The 1.62 A structure of Thermoascus aurantiacus endoglucanase: completing the structural picture of subfamilies in glycoside hydrolase family 5. L.Lo Leggio, S.Larsen. ABSTRACT
The crystal structure of Thermoascus aurantiacus endoglucanase (Cel5A), a family 5 glycoside hydrolase, has been determined to 1.62 A resolution by multiple isomorphous replacement with anomalous scattering. It is the first report of a structure in the subfamily to which Cel5A belongs. Cel5A consists solely of a catalytic module with compact eight-fold beta/alpha barrel architecture. The length of the tryptophan-rich substrate binding groove suggests the presence of substrate binding subsites -4 to +3. Structural comparison shows that two glycines are completely conserved in the family, in addition to the two catalytic glutamates and six other conserved residues previously identified. Gly 44 in particular is part of a type IV C-terminal helix capping motif, whose disruption is likely to affect the position of an essential conserved arginine. One aromatic residue (Trp 170 in Cel5A), not conserved in term of sequence, is nonetheless spatially conserved in the substrate binding groove. Its role might be to force the bend that occurs in the polysaccharide chain on binding, thus favoring substrate distortion at subsite -1.
Selected figure(s)
Figure 1.
Fig. 1. Views of molecule A in the Cel5A structure. a: Overall view of the βα-barrel with the two catalytic glutamates in ball and stick representation. 3[10] helices are shown in blue. b: View of the molecular surface with aromatic residues in color (Trp in red, Tyr in green and Phe in blue). Putative substrate binding subsites are marked. c: Conserved active site residues in GH5 shown in red (catalytic glutamates), green (aromatics) and blue (polar). The spatially conserved aromatic residues corresponding to Trp 170 are also shown for representatives of the other GH5 subfamilies: A. cellulolyticus endocellulase E1 in subfamily 1 [17]; Bacillus agaradherens endoglucanase in subfamily 2 [18]; C. thermocellum CelC in subfamily 3 [21]; C. cellulolyticum CelCCA in subfamily 4 [22]; T. fusca mannanase in subfamily 7 [15]; T. reesei mannanase in subfamily 8 [23]; C. albicans exoglucanase in subfamily 9 [16]. Cellotetraose bound to endocellulase E1 is shown for reference in yellow [17]. d: The C-terminal type IV capping motif involving Gly 44, conserved in GH5. This figure was made using the programs Molscript [51], Raster3D [52] and GRASP [53].The above figure is reprinted by permission from the Federation of European Biochemical Societies: FEBS Lett (2002, 523, 103-108) copyright 2002.
Literature references that cite this PDB file's key reference
PubMed id Reference
18755688 Y.Zhang, J.Ju, H.Peng, F.Gao, C.Zhou, Y.Zeng, Y.Xue, Y.Li, B.Henrissat, G.F.Gao, and Y.Ma (2008).
Biochemical and Structural Characterization of the Intracellular Mannanase AaManA of Alicyclobacillus acidocaldarius Reveals a Novel Glycoside Hydrolase Family Belonging to Clan GH-A.J Biol Chem, 283, 31551-31558.
PDB code: 3civ
17928686 H.W.Kim, Y.Takagi, Y.Hagihara, and K.Ishikawa (2007).
Analysis of the putative substrate binding region of hyperthermophilic endoglucanase from Pyrococcus horikoshii.Biosci Biotechnol Biochem, 71, 2585-2587.
15604820 L.Hildén, and G.Johansson (2004).
Recent developments on cellulases and carbohydrate-binding modules with cellulose affinity.Biotechnol Lett, 26, 1683-1693. 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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