This is a family of nonenzymatic polypeptides containing 60-74 amino acid residues. They contain four or five disulfide bridges of which four are conserved in all the members. Consequently, all proteins of this family show similar pattern of protein folding: three β-stranded loops extending from a central core containing the four conserved disulfide bridges. Because of their appearance, this family of proteins is called the three-finger toxin family. Our contributions to their studies are:
 
-
We have solved structure-function relationships of several toxins of three-finger family. We have identified the cytolytic, hypotensive and analgesic sites in this family of toxins. The hypotensive and analgesic peptides are covered under US patents.
- Determined the mechanism of antiplatelet effect of a cardiotoxin. We showed that cytolytic activity of this cardiotoxin is responsible for the antiplatelet effect.
- We have recently purified several novel members of this family. We have been studying their 3D structures and biological properties.
 
- We have determined the 3D structures of bucandin, bucain and bungatoxin using X-ray diffraction and NMR techniques. Their biological properties are under investigation.
- Candoxin is a unique toxin; it binds reversibly to the peripheral muscular acetylcholine receptor, but binds irreversibly to the neuronal α 7 acetylcholine receptor. We have also determined its 3D structure.
- Colubritoxin is the first toxin isolated from a ‘non venomous’ snake (Coelognathus radiatus). It is structurally similar to neurotoxin isolated from cobra venom. It reversibly blocks the peripheral acetylcholine receptor.
- We isolated and characterized two bird-specific postsynaptic neurotoxins from Boiga venoms. Denmotoxin is an irreversible inhibitor
 of neurotransmission in chick biventer cervicis muscle where as it is a highly reversible blocker of neurotransmission in mouse hemidiaphragm preparations. Similarly, irditoxin is highly toxic to chicks but not-so-toxic to mice. Denmotoxin is a monomer where as irditoxin is a heterodimer held together by a disulfide bond. We have determined the 3D structures of both these toxins.
- We isolated and characterized a new class of three-finger toxins that bind to β- adrenergic receptors and decrease the heart rate. These are the first natural, exogenous beta-blockers. They are named as
β- cardiotoxins. Its 3D structure and structure-function relationships are under investigation.
Key Publications
|
.gif){kind=spacer}
