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207 a.a.
Key reference
DOI no: 10.1107/S0907444903002051 Acta Crystallogr D Biol Crystallogr 59:765-768 (2003) PubMed id: 12657806
Structure of 20K endoglucanase from Melanocarpus albomyces at 1.8 A resolution. J.Valjakka, J.Rouvinen. ABSTRACT
The crystal structure of the 20K endoglucanase from the thermophilic fungus Melanocarpus albomyces (Ma20k) has been determined. The structure was refined to 1.8 A resolution using data obtained at 120 K. Ma20k belongs to glycoside hydrolase family 45. The three-dimensional structures of endoglucanase V (EGV) from the fungus Humicola insolens and of an endoglucanase from H. grisea var. thermoidea have previously been determined. The overall structure of Ma20k consists of a six-stranded beta-barrel domain similar to that found previously in family 45 endoglucanases. The flexible loop between strands V and VI, which was disordered in the uncomplexed structures of the Humicola endoglucanases but was ordered in complexed structures of EGV, is found to be well ordered in the native structure of Ma20k. The structure of Ma20k allows comparison between thermophilic and mesophilic proteins of family 45 and different principles for thermostability are discussed.
Selected figure(s)
Figure 3.
Figure 3 Hydrogen bonding around the catalytic donor aspartate. This residue has two alternate conformations, which are similar to the native structure of endoglucanase V. (a) Asp120 of the 20K endoglucanase from M. albomyces (Ma20k). (b) Asp121 of endoglucanase V from H. insolens (EGV). The distances (Å) between non-H atoms are given.Figure 4.
Figure 4 Superimposition of the loops between strands V and VI of the 20K endoglucanase from M. albomyces (Ma20k) and the complex structures of endoglucanase V from H. insolens (EGV). The native Ma20k is in yellow and EGV complexed with cellobiose and cellohexaose is in green and blue, respectively. The catalytic aspartates Asp10 and Asp120 and structurally important residues are labelled as in Ma20k. The superimposition of the loops was performed using O (Jones et al., 1991[Jones, T. A., Zou, J.-Y., Cowan, S. W. & Kjeldgaard, M. (1991). Acta Cryst. A47, 110-119.]) and the figure was drawn using SETOR (Evans, 1993[Evans, S. V. (1993). J. Mol. Graph. 11, 134-138.]).The above figures are reprinted by permission from the IUCr: Acta Crystallogr D Biol Crystallogr (2003, 59, 765-768) copyright 2003. Figures were selected by an automated process.
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