Substrate binding of a GH5 endoglucanase from the ruminal fungus Piromyces rhizinflata

Chih Wen Tseng, Tzu Ping Ko, Rey Ting Guo, Jian Wen Huang, Hao Ching Wang, Chun Hsiang Huang, Ya Shan Cheng, Andrew H J Wang, Je Ruei Liu

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)


The endoglucanase EglA from Piromyces rhizinflata found in cattle stomach belongs to the GH5 family of glycoside hydrolases. The crystal structure of the catalytic domain of EglA shows the (β/α)8-barrel fold typical of GH5 enzymes. Adjacent to the active site of EglA, a loop containing a disulfide bond not found in other similar structures may participate in substrate binding. Because the active site was blocked by the N-terminal His tag of a neighbouring protein molecule in the crystal, enzyme-substrate complexes could not be obtained by soaking but were prepared by cocrystallization. The E154A mutant structure with a cellotriose bound to the -3, -2 and -1 subsites shows an extensive hydrogen-bonding network between the enzyme and the substrate, along with a stacking interaction between Trp44 and the -3 sugar. A possible dimer was observed in the crystal structure, but retention of activity in the E242A mutant suggested that the enzyme probably does not function as a dimer in solution. On the other hand, the first 100 amino acids encoded by the original cDNA fragment are very similar to those in the last third of the (β/α)8-barrel fold, indicating that EglA comprises at least two catalytic domains acting in tandem.

Original languageEnglish
Pages (from-to)1189-1194
Number of pages6
JournalActa Crystallographica Section F: Structural Biology and Crystallization Communications
Issue number10
Publication statusPublished - Oct 2011
Externally publishedYes


  • carbohydrate utilization
  • catalytic domain
  • cellulase
  • molecular interactions

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Structural Biology
  • Genetics
  • Condensed Matter Physics


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