2AYH

Crystal and molecular structure at 0.16-nm resolution of the hybrid Bacillus endo-1,3-1,4-beta-D-glucan 4-glucanohydrolase H(A16-M).

(1995) Eur J Biochem 232: 849-858

• PubMed: 7588726 Search on PubMed
• Primary Citation of Related Structures:  
  2AYH


• PubMed Abstract: 
  

  H(A16-M) is a hybrid endo-1,3-1,4-beta-D-glucan 4-glucanohydrolase from Bacillus. Its crystal structure was refined using synchrotron X-ray diffraction data up to a maximal resolution of 0.16 nm. The R value of the resulting model is 14.3% against 21,032 reflections > 2 sigma. 93% of the amino acid residues are in the most favorable regions of the Ramachandran diagram, and geometrical parameters are in accordance with other proteins solved at high resolution. As shown earlier [Keitel, T., Simon, O., Borriss, R. & Heinemann, U. (1993) Proc. Natl Acad. Sci. USA 90, 5287-5291], the protein folds into a compact jellyroll-type beta-sheet structure. A systematic analysis of the secondary structure reveals the presence of two major antiparallel beta-sheets and a three-stranded minor mixed sheet. Amino acid residues involved in catalysis and substrate binding are located inside a deep channel spanning the surface of the protein. To investigate the stereochemical cause of the observed specificity of endo-1,3-1,4-beta-D-glucan 4-glucanohydrolases towards beta-1,4 glycosyl bonds adjacent to beta-1,3 bonds, the high-resolution crystal structure has been used to model an enzyme-substrate complex. It is proposed that productive substrate binding to the subsites p1, p2 and p3 of H(A16-M) requires a beta-1,3 linkage between glucose units bound to p1 and p2.

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Organizational Affiliation: 

Forschungsgruppe Kristallographie, Max-Delbrück-Centrum für Molekulare Medizin, Berlin, Germany.