TABLE 26.1

Comparison of the two major classes of glycan-binding proteins

LectinsaGlycosaminoglycan-binding proteinsb
Shared evolutionary originsyes (within each group)no
Shared structural featuresyes (within each group)no
Defining AA residues involved in bindingoften typical for each grouppatch of basic amino acid residues
Type of glycans recognizedN-glycans, O-glycans, glycosphingo-lipids (a few also recognize sulfated glycosaminoglycans)different types of sulfated glycosaminoglycans
Location of cognate residues within glycanstypically in sequences at outer ends of glycan chainstypically in sequences internal to an extended sulfated glycosaminoglycan chain
Specificity for glycans recognizedstereospecificity high for specific glycan structuresoften recognize a range of related sulfated glycosaminoglycan structures
Single-site binding affinityoften low; high avidity generated by multivalencyoften moderate to high
Valency of binding sitesmultivalency common (either within native structure or by clustering)often monovalent
SubgroupsC-type lectins, galectins, P-type lectins, I-type lectins, L-type lectins, R-type lectins etc.heparan sulfate–binding proteins, chondroitin sulfate–binding proteins, dermatan sulfate– binding proteins
Types of glycans recognized within each groupcan be similar (e.g., galectins) or variable (e.g., C-type lectins)classification itself is based on type of glycosaminoglycan chain recognized

Modified from Varki A. and Angata T. 2006. Glycobiology 16: 1R–27R.

a

There are other animal proteins that recognize glycans in a lectin-like manner and do not appear to fall into one of the well-recognized classes (e.g., various cytokines).

b

Hyaluronan (HA)-binding proteins (hyaloadherins) fall in between these two classes. On the one hand, some (but not all) of the hyaloadherins have shared evolutionary origins. On the other hand, recognition involves internal regions of HA, which is a nonsulfated glycosaminoglycan.

There are other animal proteins that recognize glycans in a lectin-like manner and do not appear to fall into one of the well-recognized classes (e.g., various cytokines).

Hyaluronan (HA)-binding proteins (hyaloadherins) fall in between these two classes. On the one hand, some (but not all) of the hyaloadherins have shared evolutionary origins. On the other hand, recognition involves internal regions of HA, which is a nonsulfated glycosaminoglycan.

From: Chapter 26, Discovery and Classification of Glycan-Binding Proteins

Cover of Essentials of Glycobiology
Essentials of Glycobiology. 2nd edition.
Varki A, Cummings RD, Esko JD, et al., editors.
Cold Spring Harbor (NY): Cold Spring Harbor Laboratory Press; 2009.
Copyright © 2009, The Consortium of Glycobiology Editors, La Jolla, California.

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