Multivalency in Lectins M Vijayan Molecular Biophysics Unit
Multivalency in Lectins M. Vijayan Molecular Biophysics Unit Indian Institute of Science Bangalore 560012
Plant Lectin Families I Legume lectins Jelly roll II Cereal lectins Hevein domain III Moraceae lectins -prism I IV Bulb lectins -prism II V -trefoil Ricin, Amaranthin etc
Legume lectins: peanut lectin, winged bean basic and acidic lectins and their complexes Peanut lectin (PNA) Tetramer, Mr 1, 10, 000; Non-glycosylated; galactose specific; specific to T-antigen (Gal 1 -3 Gal. NAc) at disaccharide level Basic winged bean lectin (WBA I) Dimer, Mr 58, 000; glycosylated; Gal/Gal. NAc specific; specific to blood group A and less to B, does not bind O Acidic winged bean lectin (WBA II) Dimer, Mr 58, 000; glycosylated; Gal/Gal. NAc specific; specific to blood group O and binds weakly to A and B
Legume lectins: peanut lectin, winged bean basic and acidic lectins and their complexes • PNAS (1994) 91, 227 -231 • JMB (1996) 259, 281 -291 • JBC (1996) 271, 21209 -21213 • Curr. Sci. (1997) 72, 855 -861 • JMB (1998) 276, 787 -796 • Glycobiology (1998) 10, 1007 -1012 • JACS (1998) 120, 11297 -11303 • Proteins SFG (1999) 35, 58 -69 • Acta Cryst. (1999) D 55, 1375 -1382 • JMB (2000) 302, 1129 -1137 • Proteins SFG (2001) 43, 260 -270 • JBC (2001) 276, 40734 -40739 • Protein Eng. (2001) 14, 857 -866 • Acta Cryst. (2001) D 57, 1584 -1594 • Acta Cryst. (2003) D 59, 2254 -2256
Legume lectins: peanut lectin, winged bean basic and acidic lectins and their complexes • Multimeric proteins can assume open quaternary structures • High variability in quaternary structure while the tertiary structure is essentially same • Water bridges as a strategy for generating ligand specificity • Role of loop length and aromatic interactions in generating carbohydrate specificity • Structure-based mutational studies
Jackfruit
Jacalin: A lectin from jackfruit seeds Nat. Struct. Biol. (1996) 3, 596 -603 J. Mol. Biol. (2002) 321, 637 -645 J. Mol. Biol. (2003) 332, 217 -228 • Tetramer, Mr 66, 000; glycosylated; Gal/Gal. NAc specific; Specific to Tantigen at disaccharide level • New lectin fold characteristic of the moraceae family
Hydrogen-bonding interactions between jacalin and galactose • Post translational proteolysis is used as a strategy for generating ligand specificity
Composite view of binding region Secondary site A Secondary site B Primary site
Structure and interactions of artocarpin J. Mol. Biol (2002) 317, 237 -247 J. Mol. Biol (2004) 338, 757 -770 • Tetrameric, Mr 65, 000; • Non-glycosylated; • Mannose-specific
Snake gourd
Structure of snake gourd lectin Acta Cryst. (2001) D 57, 912 -914 • Heterodimeric, Mr 62, 000; Glycosylated; Galactose specific • Amino acid sequence not available • Structure similar to that of type. II RIP’s
Snake gourd lectin has no ribosome inactivating property Red SGSL Blue Trichosanthin
Structure and interactions of garlic lectin JMB (1999) 285, 1157 -1168 • Dimeric, Mr 24, 000; • Non-glycosylated; • Mannose specific
Garlic lectin: Re-refinement using reprocessed data G. Ramachandraiah, Nagasuma R. Chandra, A. Surolia and M. Vijayan (2002) Acta Cryst. D 58, 414 -420 XDS DENZO X-PLOR CNS • Resolution increased from 2. 8Å (effective) to 2. 2Å • Isolectins could be identified with confidence • Asymmetric unit contains two heterodimers. Better definition of the structure
Garlic lectin-olygosaccharide interactions G. Ramachandraiah, Nagasuma R. Chandra, A. Surolia and M. Vijayan (2003) Glycobiology 13, 765 -775 11. 6 8. 6 2 NI 7. 3 4 Man 1 -2 Man 1 -3 Man 29. 0 Man 3 6 Man 1 -4 Man 1 -6 Man 28. 8 Man 5
Man 7 Gn 2 Asn 6545 M 7 N 8 N 9 M 6 7200 Man 8 Gn 2 Asn M 5 M 8 M 7 M 6 14120 Man 9 Gn 2 Asn N 9 N 10
Single cross-linking • • • Tri : 6 × 6: 36 Penta : 12 × 6: 72 Hepta : 12 × 6: 72 Octa : 12 × 6: 72 Nona : 12 × 6: 72 Accepted pairs of dimers: Short contacts <=20
Double cross-linking Term. pairs: 12 C 2 Site pairs: 6 P 2 Total: 12 C 2 × 6 P 2 : 1980 |Tij-Sij| <=3. 0 Å Accepted pairs of dimers: Short contacts <=40
Tri Penta Hepta Octa Nona No. of Single links No. of Double links 24 24 70 61 94 3 7 36 20 64
M 1 F-M 3 E
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