¹H NMR study of the interaction ofN,N′,N″‐triacetyl chitotriose with Ac‐AMP2, a sugar binding antimicrobial protein isolated fromAmaranthus caudatus

The interaction between Ac-AMP2, a lectin-like small protein with antimicrobial and antifungal activity isolated from Amaranthus caudatus, and N,N',N"-triacetyl chitotriose was studied using 1H NMR spectroscopy. Changes in chemical shift and line width upon increasing concentration 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 association constant Ka. The most pronounced shifts occur mainly in the C-terminal half of the sequence. They involve the aromatic residues Phe18, Tyr20 and Tyr27 together with their surrounding residues, as well as the N-terminal Val-Gly-Glu segment. Several NOEs between Ac-AMP2 and the N,N',N"-triacetyl chitotriose resonances are reported.