An important approach to
understanding the roles of mammalian carbohydrate-binding proteins is to
examine the functions of orthologs in simpler organisms.
Because of the advanced state of the developmental, genetic and
genomic study of Caenorhabditis
elegans and Drosophila
melanogaster, these organisms are particularly attractive models.
Homologs of six classes of lectins have been identified using
methods of sequence comparisons combined with knowledge of how these
proteins interact with glycan ligands.
The results have been described in the two references below.
With regard to C-type
lectin-like domains, relative to genome size there are far more CTLDs in the model
invertebrates than in mammals. However,
the C elegans and Drosophila
proteins that contain CTLDs are quite distinct from the mammalian proteins
that contain CTLDs. These
differences are evident in the sequences of the CTLDs and the domain
organization of the proteins in which they are found.
Only a small subset of invertebrate CTLDs contain the constellation
of amino acid residues that form Ca2+-
and sugar-binding sites in mammalian C-type carbohydrate-recognition
domains.
For further information see:
Drickamer, K and Dodd, RB (1999) C-type lectin-like domains in Caenorhabditis elegans: predictions from the complete genome sequence. Glycobiology, 9, 1357-1369. PDF version.
Dodd, RB and Drickamer, K (2001) Lectin-like proteins in model organisms: implications for evolution of carbohydrate-binding activity. Glycobiology, 11, 71R-79R PDF version.
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