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

Jackfruit

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

Composite view of binding region

Primary site

Secondary site B

Secondary site A

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

Snake gourd

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

Snake gourd lectin has no ribosome inactivating property

Red SGSLBlue 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. 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

M5

M6M7

N8 N9N8

M5

M6M7M8

N9 N10

Man9Gn2Asn

Man8Gn2Asn

Man7Gn2Asn

14120

7200

6545

• 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

No. of Single links

No. of Double links

TriPentaHeptaOctaNona

2424706194

37362064

M1F-M3E