Post on 14-Dec-2015
Multivalency in Lectins
M. Vijayan
Molecular Biophysics UnitIndian 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 Ricin, Amaranthin etc -trefoil
Legume lectins: peanut lectin, winged bean basic and acidic lectins and their complexes
Basic winged bean lectin (WBA I)
Dimer, Mr 58,000; glycosylated; Gal/GalNAcspecific; 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/GalNAcspecific; specific to blood group O and binds weakly to A and B
Peanut lectin (PNA)
Tetramer, Mr 1,10,000; Non-glycosylated;galactose specific; specific to T-antigen (Gal1-3GalNAc) at disaccharide level
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) D55, 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) D57, 1584-1594• Acta Cryst. (2003) D59, 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
Jacalin: A lectin from jackfruit seeds
• Tetramer, Mr 66,000; glycosylated; Gal/GalNAc specific; Specific to T-antigen at disaccharide level• New lectin fold characteristic of the moraceae family
Nat. Struct. Biol. (1996) 3, 596-603 J. Mol. Biol. (2002) 321, 637-645 J. Mol. Biol. (2003) 332, 217-228
Hydrogen-bonding interactions between jacalin and galactose
• Post translational proteolysis is used as a strategy for generating ligand specificity
Structure and interactions of artocarpin
J. Mol. Biol (2002) 317, 237-247J. Mol. Biol (2004) 338,757-770
• Tetrameric, Mr 65,000;
• Non-glycosylated;
• Mannose-specific
Structure of snake gourd lectin
Acta Cryst. (2001) D57, 912-914
• Heterodimeric, Mr 62,000; Glycosylated; Galactose specific
• Amino acid sequence not available
• Structure similar to that of typeII RIP’s
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. D58, 414-420
XDS X-PLORDENZO 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 interactionsG. Ramachandraiah, Nagasuma R. Chandra, A. Surolia and M. Vijayan(2003) Glycobiology 13, 765-775
Man1-2Man
2 64
Man1-3Man Man1-4Man Man1-6Man
Man3 Man5
8.6 11.6 NI 7.3
28.829.0
• 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
Single cross-linking
Term. pairs: 12C2
Site pairs: 6P2
Total: 12C2 × 6P2
:1980
|Tij-Sij| <=3.0 Å
Accepted pairs of dimers:Short contacts <=40
Double cross-linking