The crystal structure of the catalytic core domain of endoglucanase I from Trichoderma reesei at 3.6 Å resolution, and a comparison with related enzymes

Gerard Kleywegt, Jinyu Zou, Christina Divne, G. Davies, Irmgard Sinning, Jerry Ståhlberg, Tapani Reinikainen, Malee Srisodsuk, Tuula Teeri, T. Alwyn Jones (Corresponding Author)

Research output: Contribution to journalArticleScientificpeer-review

207 Citations (Scopus)


Cellulose is the most abundant polymer in the biosphere. Although generally resistant to degradation, it may be hydrolysed by cellulolytic organisms that have evolved a variety of structurally distinct enzymes, cellobiohydrolases and endoglucanases, for this purpose. Endoglucanase I (EG I) is the major endoglucanase produced by the cellulolytic fungus Trichoderma reesei, accounting for 5 to 10% of the total amount of cellulases produced by this organism. Together with EG I from Humicola insolens and T. reesei cellobiohydrolase I (CBH I), the enzyme is classified into family 7 of the glycosyl hydrolases, and it catalyses hydrolysis with a net retention of the anomeric configuration.

The structure of the catalytic core domain (residues 1 to 371) of EG I from T. reesei has been determined at 3.6 Å resolution by the molecular replacement method using the structures of T. reesei CBH I and H. insolens EG I as search models. By employing the 2-fold non-crystallographic symmetry (NCS), the structure was refined successfully, despite the limited resolution. The final model has an R-factor of 0.201 (Rfree 0.258).

The structure of EG I reveals an extended, open substrate-binding cleft, rather than a tunnel as found in the homologous cellobiohydrolase CBH I. This confirms the earlier proposal that the tunnel-forming loops in CBH I have been deleted in EG I, which has resulted in an open active site in EG I, enabling it to function as an endoglucanase. Comparison of the structure of EG I with several related enzymes reveals structural similarities, and differences that relate to their biological function in degrading particular substrates. A possible structural explanation of the drastically different pH profiles of T. reesei and H. insolens EG I is proposed.

Original languageEnglish
Pages (from-to)383-397
JournalJournal of Molecular Biology
Issue number3
Publication statusPublished - 1997
MoE publication typeA1 Journal article-refereed


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