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8.B.9.1.1
Cycseine-rich venom protein, Triflin.  Blocks contraction of smooth muscle elicited by high potassium-induced depolarization.  May also target voltage-gated calcium channels (Cav) in smooth muscle cells.  The crystal structure of triflin, a snake venom derived blocker of high K+-induced artery contraction has been solved at 2.4A resolution. Triflin consists of two domains. The first 163 residues form a large globular body with an αβα sandwich core which resembles pathogenesis-related proteins of group-1 (PR-1). Two glutamic acid-associated histidine residues are located in an elongated cleft. A Cd2+ resides in this binding site, and forms a five-coordination sphere. The subsequent cysteine-rich domain adopts a rod-like shape, which is stabilized by five disulfide bridges. Hydrophobic residues, which may obstruct the target ion channel, are exposed to the solvent. A concave surface, which is surrounded by these two domains, may play a role in the binding to the target receptor, leading to ion channel blockage. The C-terminal cysteine-rich region has a similar tertiary structure to voltage-gated potassium channel blocker toxins such as BgK and ShK (Shikamoto et al. 2005).

Accession Number:Q8JI39
Protein Name:Triflin
Length:240
Molecular Weight:26752.00
Species:Trimeresurus flavoviridis (Habu) (Protobothrops flavoviridis) [88087]
Location1 / Topology2 / Orientation3: Secreted1
Substrate NONE

Cross database links:

Pfam: PF08562    PF00188   

Gene Ontology

GO:0005576 C:extracellular region
GO:0019855 F:calcium channel inhibitor activity
GO:0009405 P:pathogenesis

References (3)

[1] “Cloning and characterization of novel snake venom proteins that block smooth muscle contraction.”  Yamazaki Y.et.al.   12047379
[2] “Identification of novel serum proteins in a Japanese viper: homologs of mammalian PSP94.”  Aoki N.et.al.   17543280
[3] “Crystal structure of a CRISP family Ca2+ -channel blocker derived from snake venom.”  Shikamoto Y.et.al.   15953617
Structure:
1WVR     

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FASTA formatted sequence
1:	MIAFIVLPIL AAVLQQSSGN VDFDSESPRK PEIQNEIIDL HNSLRRSVNP TASNMLKMEW 
61:	YPEAAANAER WAYRCIESHS SRDSRVIGGI KCGENIYMAT YPAKWTDIIH AWHGEYKDFK 
121:	YGVGAVPSDA VIGHYTQIVW YKSYRAGCAA AYCPSSKYSY FYVCQYCPAG NIIGKTATPY 
181:	KSGPPCGDCP SDCDNGLCTN PCTRENEFTN CDSLVQKSSC QDNYMKSKCP ASCFCQNKII