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Multivalency in Lectins M. Vijayan Molecular Biophysics Unit Indian Institute of Science Bangalore 560012.

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Presentation on theme: "Multivalency in Lectins M. Vijayan Molecular Biophysics Unit Indian Institute of Science Bangalore 560012."— Presentation transcript:

1 Multivalency in Lectins M. Vijayan Molecular Biophysics Unit Indian Institute of Science Bangalore 560012

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3 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

4 Legume lectins: peanut lectin, winged bean basic and acidic lectins and their complexes Basic winged bean lectin (WBA I) Dimer, M r 58,000; glycosylated; Gal/GalNAc specific; specific to blood group A and less to B, does not bind O Acidic winged bean lectin (WBA II) Dimer, M r 58,000; glycosylated; Gal/GalNAc specific; specific to blood group O and binds weakly to A and B Peanut lectin (PNA) Tetramer, M r 1,10,000; Non-glycosylated; galactose specific; specific to T-antigen (Gal  1-3GalNAc) at disaccharide level

5 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

6 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

7 Jackfruit

8 Jacalin: A lectin from jackfruit seeds Tetramer, M r 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

9 Hydrogen-bonding interactions between jacalin and galactose Post translational proteolysis is used as a strategy for generating ligand specificity

10 Composite view of binding region Primary site Secondary site B Secondary site A

11 Structure and interactions of artocarpin J. Mol. Biol (2002) 317, 237-247 J. Mol. Biol (2004) 338,757-770 Tetrameric, M r 65,000; Non-glycosylated; Mannose-specific

12 Snake gourd

13 Structure of snake gourd lectin Acta Cryst. (2001) D57, 912-914 Heterodimeric, M r 62,000; Glycosylated; Galactose specific Amino acid sequence not available Structure similar to that of typeII RIP’s

14 Snake gourd lectin has no ribosome inactivating property Red SGSL Blue Trichosanthin

15 Structure and interactions of garlic lectin JMB (1999) 285, 1157-1168 Dimeric, M r 24,000; Non-glycosylated; Mannose specific

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17 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-PLOR DENZO 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

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19 Garlic lectin-olygosaccharide interactions G. Ramachandraiah, Nagasuma R. Chandra, A. Surolia and M. Vijayan (2003) Glycobiology 13, 765-775 Man  1-2Man 264 Man  1-3Man Man  1-4ManMan  1-6Man Man3 Man5 8.6 11.6NI7.3 28.8 29.0

20 M5 M6 M7 N8 N9 N8 M5 M6 M7 M8 N9 N10 Man9Gn2Asn Man8Gn2Asn Man7Gn2Asn 14120 7200 6545

21 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

22 Term. pairs: 12 C 2 Site pairs: 6 P 2 Total: 12 C 2 × 6 P 2 :1980 |T ij -S ij | <=3.0 Å Accepted pairs of dimers: Short contacts <=40 Double cross-linking

23 No. of Single links No. of Double links Tri Penta Hepta Octa Nona 24 70 61 94 3 7 36 20 64

24 M1F-M3E

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