Triflin is a

cysteine-rich secretory protein Cysteine-rich secretory proteins, often abbreviated as CRISPs, are a group of glycoproteins. They are a subgroup of the CRISP, antigen 5 and Pr-1 ( CAP) protein superfamily and also contain a domain related to the ShK toxins. They are substantiall ...

(CRISP), which is excreted by the

venom Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...

gland of the Habu snake (''

Trimeresurus flavoviridis ''Protobothrops flavoviridis'' is a species of venomous pit viper endemic to the Ryukyu Islands of Japan. No subspecies are currently recognized. Local common names include habu,Gumprecht A, Tillack F, , Captain A, Ryabov S. 2004. ''Asian Pitvipe ...

''). Triflin reduces high potassium-induced smooth muscle contraction, suggesting a blocking effect on

L-type calcium channel The L-type calcium channel (also known as the dihydropyridine channel, or DHP channel) is part of the high-voltage activated family of voltage-dependent calcium channel. "L" stands for long-lasting referring to the length of activation. This c ...

Sources

Triflin is a toxin derived from snake venom. The toxin is produced in the gland of the Habu snake, ''

''.

Chemistry

Triflin is a cysteine-rich secretory protein, which means it belongs to the CRISP family. This is a group of single chain polypeptides found in various organisms. Triflin weighs 25 kDa and consists of 221

amino-acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha ami ...

residues. The first 163 residues of the

N-terminal The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide, referring to the free amine group (-NH2) located at the end of a polypeptide. Within a peptide, the ami ...

domain forms an α-β-α sandwich core. This domain is comparable with group 1 plant

pathogenesis-related protein Pathogenesis-related (PR) proteins are proteins produced in plants in the event of a pathogen attack. They are induced as part of systemic acquired resistance. Infections activate genes that produce PR proteins. Some of these proteins are antimicro ...

(PR-1). The

C-terminal The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain (protein or polypeptide), terminated by a free carboxyl group (-COOH). When the protein is ...

domain, has five

disulfide bridges In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In ...

. This domain is responsible for the selectivity of the protein and consists of two subdomains: N-terminal subdomain (Cys 167 to Cys 179) and C-terminal subdomain (42 amino-acids residues). The N-terminal subdomain is connected with N-terminal domain through two main-chain

hydrogen bond In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a ...

s between β11 and β2 and is thereby part of the PR-1 domain. The C-terminal subdomain is stabilized by three disulfide bridges and it is remarkable that this domain does not interact with either the PR-1 domain or the N-terminal sub-domain. The C-terminal subdomain consists of particles, including some hydrophobic residues that are exposed to the solvent. These hydrophobic residues might mediate the interaction with the target proteins and therefore receptor recognition. There are some homologous toxins to Triflin with different percentages of amino-acid sequence similarity, such as

Ablomin Ablomin is a toxin present in the venom of the Japanese Mamushi snake, which blocks L-type voltage-gated calcium channels. Etymology The protein ablomin is a component of the venom of the Japanese Mamushi snake, ''Gloydius blomhoffii''. The ter ...

Latisemin Latisemin is a cysteine-rich secretory protein that can be isolated from the venom of the Black-banded sea krait, a sea snake indigenous to the warmer waters of the western Pacific Ocean. It is a toxin that inhibits cyclic nucleotide-gated ion ch ...

, Stecrip (88%), Helothermine (49%), Pseudechetoxin (62%), Pseudesin (61%). The snake venoms which belong to CRISP family seem to be homologous to each other, however there are differences in their protein targets.

Target

Triflin reduces high potassium induced smooth muscle contraction, suggesting a blocking effect on

Treatment

One of the small serum proteins (SSP-2), a substance produced by ''

'' itself, has high affinity for Triflin, and may thus work as a defensive mechanism against accidental self-poisoning, suggesting a possible role for SSP-2 as an antidote to triflin.

References

{{reflist Ion channel toxins

Sources

Chemistry

Target

Treatment

See also

References