Payan, F ; Flatman, R ; Porciero, S ; Williamson, G ; Juge, N ; Roussel, A
Biochemical Journal 372 399-405 Part 2
A novel class of proteinaceous inhibitors exhibiting specificity towards microbial xylanases has recently been discovered in cereals. The three-dimensional structure of xylanase inhibitor protein I (XIP-1) from wheat (Triticum aestivum, var. Soisson) was determined by X-ray crystallography at 1.8 Angstrom (1 Angstrom = 0.1 mn) resolution. The inhibitor possesses a (√ü/a)(8) barrel fold and has structural features typical of glycoside hydrolase family 18, namely two consensus regions, approximately corresponding to the third and fourth barrel strands, and two non-proline cis-peptide bonds, Ser(36)-Phe and Trp(256)-Asp (in XIP-I numbering). However, detailed structural analysis of XIP-I revealed several differences in the region homologous with the active site of chitinases.