H-1-NMR STUDY OF THE INTERACTION OF N,N',N''-TRIACETYL CHITOTRIOSE WITH AC-AMP2, A SUGAR BINDING ANTIMICROBIAL PROTEIN ISOLATED FROM AMARANTHUS-CAUDATUS

The interaction between Ac-AMP2, a lectin-like small protein with anti microbial and antifungal activity isolated from Amaranthus caudatas, a nd N,N',N ''-triacetyl chitotriose was studied using H-1 NMR spectrosc opy, Changes in chemical shift and line width upon increasing concentr ation of N,N',N ''-triacetyl chitotriose to Ac-AMP2 solutions at pH 6. 9 and 2.4 were used to determine the interaction site and the associat ion constant K-a. The most pronounced shifts occur mainly in the C-ter minal half of the sequence, They involve the aromatic residues phe(18) , Tyr(20) and Tyr(27) together with their surrounding residues, as wel l as the N-terminal Val-Gly-Glu segment, Several NOEs between Ac-AMP2 and the N,N',N ''-triacetyl chitotriose resonances are reported.