PREPARATION OF A PHOTOACTIVATABLE FLUORESCENT DERIVATIVE OF LACTOSE AND ITS APPLICATION TO PHOTOAFFINITY-LABELING OF A CONGER EEL LECTIN

A photoactivatable heterobifunctional fluorescent reagent, 1-azido-5-n aphthalene sulfonyl (ANS) hydrazide, was synthesized and characterized . ANS-hydrazide reacted with lactose to form a photoactivatable hydraz one. The derivative (ANS-lactose) had the same binding affinity for a conger eel lectin as lactose judging from the hemagglutinating-inhibit ion assay with rabbit erythrocytes. ANS-lactose was used for photoaffi nity labeling of a conger eel lectin. The photolabeled lectin was dige sted with chymotrypsin to isolate photolabeled peptides by reversed-ph ase HPLC by monitoring fluorescence. A major labeled peptide was locat ed at positions 31-45 in the lectin by amino acid analysis and N-termi nal sequencing. The identified segment was close to the highly conserv ed region throughout animal beta-galactoside-binding lectins.