STRUCTURAL MODEL FOR FAMILY 32 OF GLYCOSYL-HYDROLASE ENZYMES

A structural model is presented for family 32 of the glycosyl-hydrolas e enzymes based on the beta-propeller fold. The model is derived from the common prediction of two different threading methods, TOPITS and T HREADER. In addition, we used a correlated mutation analysis and predi ction of active-site residues to corroborate the proposed model. Physi cal techniques (circular dichroism and differential scanning calorimet ry) confirmed two aspects of the prediction, the proposed all-beta fol d and the multi-domain structure. The most reliable three-dimensional model was obtained using the structure of neuraminidase (1nscA) as tem plate. The analysis of the position of the active site residues in thi s model is compatible with the catalytic mechanism proposed by Reddy a nd Maley (J, Biol. Chem, 271:13953-13958, 1996), which includes three conserved residues, Asp, Glu, and Cys. Based on this analysis, we prop ose the participation of one more conserved residue (Asp 162) in the c atalytic mechanism. The model will facilitate further studies of the p hysical and biochemical characteristics of family 32 of the glycosyl-h ydrolases, Proteins 33:383-395, 1998, (C) 1998 Wiley-Liss,Inc.