Presentation is loading. Please wait.

Presentation is loading. Please wait.

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

Similar presentations


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

2

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, JMB (1996) 259, JBC (1996) 271, Curr. Sci. (1997) 72, JMB (1998) 276, Glycobiology (1998) 10, JACS (1998) 120, Proteins SFG (1999) 35, Acta Cryst. (1999) D55, JMB (2000) 302, Proteins SFG (2001) 43, JBC (2001) 276, Protein Eng. (2001) 14, Acta Cryst. (2001) D57, Acta Cryst. (2003) D59,

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, J. Mol. Biol. (2002) 321, J. Mol. Biol. (2003) 332,

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, J. Mol. Biol (2004) 338, Tetrameric, M r 65,000; Non-glycosylated; Mannose-specific

12 Snake gourd

13 Structure of snake gourd lectin Acta Cryst. (2001) D57, 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, Dimeric, M r 24,000; Non-glycosylated; Mannose specific

16

17 Garlic lectin: Re-refinement using reprocessed data G. Ramachandraiah, Nagasuma R. Chandra, A. Surolia and M. Vijayan (2002) Acta Cryst. D58, 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

18

19 Garlic lectin-olygosaccharide interactions G. Ramachandraiah, Nagasuma R. Chandra, A. Surolia and M. Vijayan (2003) Glycobiology 13, Man  1-2Man 264 Man  1-3Man Man  1-4ManMan  1-6Man Man3 Man NI

20 M5 M6 M7 N8 N9 N8 M5 M6 M7 M8 N9 N10 Man9Gn2Asn Man8Gn2Asn Man7Gn2Asn

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 M1F-M3E

25

26


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

Similar presentations


Ads by Google