High-resolution crystal structures reveal how a cellulose chain is bound in the 50 angstrom long tunnel of cellobiohydrolase I from Trichoderma reesei

C Divne, J Stahlberg, TT Teeri, TA Jones*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Detailed information has been obtained, by means of protein X-ray crystallography, on how a cellulose chain is bound in the cellulose-binding tunnel of cellobiohydrolase I (CBHI), the major cellulase in the hydrolysis of native, crystalline cellulose by the fungus Trichoderma reesei. Three high-resolution crystal structures of different catalytically deficient mutants of CBHI in complex with cellotetraose cellopentaose and cellohexaose have been refined at 1.9, 1.7 and 1.9 Angstrom resolution, respectively. The observed binding of cellooligomers in the tunnel allowed unambiguous identification of ten well-defined subsites for glucosyl units that span a length of similar to 50 Angstrom. All bound oligomers have the same directionality and orientation, and the positions of the glucosyl units in each binding site agree remarkably well between the different complexes. The binding mode observed here corresponds to that expected during productive binding of a cellulose chain. The structures support the hypothesis that hydrolysis by CBHI proceeds from the reducing towards the non-reducing end of a cellulose chain, and they provide a structural explanation for the observed distribution of initial hydrolysis products. (C) 1998 Academic Press Limited.

Original languageEnglish
Pages (from-to)309-325
Number of pages17
JournalJOURNAL OF MOLECULAR BIOLOGY
Volume275
Issue number2
Publication statusPublished - 16 Jan 1998
MoE publication typeA1 Journal article-refereed

Keywords

  • cellulase
  • cellobiohydrolase
  • oligosaccharide complex
  • active-site mutant
  • crystal structure
  • ACID-SEQUENCE SIMILARITIES
  • ELECTRON-DENSITY MAPS
  • FREE R-VALUE
  • BINDING DOMAIN
  • 3-DIMENSIONAL STRUCTURE
  • QM-9414
  • MODEL
  • IDENTIFICATION
  • CLASSIFICATION
  • REFINEMENT

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