Abstract
The plant lectin Tetracarbidium conophorum agglutinin II binds to glycoproteins and glycopeptides in a structurally specific manner [Animashaun et al., (1994) Glycoconjugate J. 11, 299-303]. We have characterized the steady-state and time-resolved fluorescence of the tryptophan residues of this lectin. The fluorescence (λ ex = 295 nm, λ em = 350 nm) decay is complex and can be described by four decay times with the following values: τ 1 = 7.4 nsec, α 1 = 0.22; τ 2 = 2.9 nsec, α 2 = 0.25; τ 3 = 1.0 nsec, α 3 = 0.34; τ 4 = 0.2 nsec, α 4 = 0.18. The addition of a biantennary glycopeptide (Chemical Equation Presented) to the lectin results in a quench and an 8 nm blue shift of the emission spectrum. The effect is saturable, and is described by an association constant of 1.8 x 10 5 M -1 . The tryptophan fluorescence of Tetracarbidium conophorum agglutinin II may therefore be utilized to characterize thermodynamically the binding interactions between this lectin and complex glycoprotein. © 1998 Plenum Publishing Corporation.