Primary structure and kinetic interaction with glycoproteins of the lectin from seeds of Cratylia floribunda

The complete 236-amino-acid sequence of the glucose/mannose specific lectin from seeds of Cratylia floribunda (CFL) was determined by automated Edman sequencing of overlapping proteolytic peptides purified by HPLC after digestion of the lectin with endoproteinases Lys-C, Asp-N, trypsin and chymotrypsin. Mass spectrometry confirmed the sequence analysis and showed that CFL consists of a mixture of full length, single-chain polypeptide (alpha-chain. 25397 +/- 3 Da) and its' noncovalently associated beta (residues 1-118, 12847 +/- 2 Da) and gamma (residues 119-236, 12568 +/- 1 Da) fragments. The primary structure of Cratylia floribunda lectin has extensive amino acid sequence homology with those of lectins from species of the taxonomically related genera Canavalia and Dioclea. However, using surface plasmon resonance, CFL and ConA, the seed lectin from Canavalia ensiformis, displayed distinct kinetic interactions with glycoproteins, indicating structural differences in their extended glycan binding-sites.