Structural highlights
Publication Abstract from PubMedLectins are carbohydrate-binding proteins that exert their biological activity by binding to specific cell glycoreceptors. We have expressed CNL, a ricin B-like lectin from the basidiomycete Clitocybe nebularis, in Escherichia coli. The recombinant lectin, rCNL, agglutinates human blood group A erythrocytes and is specific for the unique glycan N,N'-diacetyllactosediamine (GalNAcbeta1-4GlcNAc, LacdiNAc, LDN) as demonstrated by glycan microarray analysis. We here describe the crystal structures of rCNL in complex with lactose and LDN, defining its interactions with the sugars. CNL is a homodimeric lectin, each of whose monomers comprises a single ricin B lectin domain with its beta-trefoil fold and one carbohydrate-binding site. In order to study the mode of CNL action, a non-sugar-binding mutant and non-dimerizing monovalent mutants that retain carbohydrate-binding activity were prepared. rCNL and the mutants were examined for their biological activities against Jurkat human leukemic T cells and the hypersensitive nematode Caenorhabditis elegans mutant strain pmk-1. rCNL was toxic against both, while the mutants were inactive. Thus, the bivalent carbohydrate-binding property of homodimeric CNL is essential for its activity, providing one of the rare pieces of evidence that certain activities of lectins are associated with their multivalency. Bivalent carbohydrate binding is required for biological activity of CNL, the LacdiNAc (GalNAcbeta1-4GlcNAc)-specific lectin from basidiomycete Clitocybe nebularis.,Pohleven J, Renko M, Magister S, Smith DF, Kuenzler M, Strukelj B, Turk D, Kos J, Sabotic J J Biol Chem. 2012 Feb 1. PMID:22298779[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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