Transcript galactose specific

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1-3GalNAc) at disaccharide level
Basic winged bean lectin (WBA I)
Dimer, Mr 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, Mr 58,000; glycosylated; Gal/GalNAc
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) 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
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/GalNAc
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) 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 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. D58, 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1-2Man
Man1-3Man
29.0
Man3
6
Man1-4Man
Man1-6Man
28.8
Man5
Man7Gn2Asn
6545
M5
M7
N8
N9
M6
7200
Man8Gn2Asn
M5
M8
M7
M6
14120
Man9Gn2Asn
N9
N10
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: 12C2
Site pairs: 6P2
Total: 12C2 × 6P2
: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
M1F-M3E