Identification of a carbohydrate‐binding site in physarum haemagglutinin I

Abstract

Carbohydrate‐binding peptides from trypsin‐digests of Physarum lectins (haemagglutinins I and II) were isolated by affinity column chromatography. The amino acid sequence of the peptlde fragment from haemagglutinin I was determined to be 48TVHQSWY54. A similar amino acid sequence was found in the peptide fragment from haemagglutinin II, in which alignment of valine, histidine, tryptophan and tyrosine was identical. Deletion of the heptapeptide sequence (TVHQSWY) by site‐directed mutation abolished the haemagglutinating activity. The replacement of Trp53 by alanine resulted in a complete loss of the haemagglutinating activity, suggesting that the tryptophan residue in the heptapeptide sequence is essential for carbohydrate binding.

The Structure of Physarum polycephalum Hemagglutinin I Suggests a Minimal Carbohydrate Recognition Domain of Legume Lectin Fold

“…This idea is consistent with previous data showing that residues T49 to Y55 of HA1 are essential for HA1-glycoprotein interaction. 11 In general, some aromatic residues, especially tryptophans and tyrosines, of CBMs form a hydrophobic surface patch for binding to the pyranose rings of sugar chains on the target carbohydrates. [20][21][22][23] In addition, hydroxyl groups of carbohydrates form hydrogen bonds with polar residues of CBMs.…”