Piscivorin
Piscivorin is a component of snake venom secreted by the Eastern Cottonmouth (Agkistrodon piscivorus piscivorus).[1] It is a member of the cysteine-rich secretory protein (CRISP) family, which blocks voltage-dependent calcium channels.
Etymology
[edit]The name of piscivorin comes from the snake species name piscivorus, which is derived from the Latin words pisces and vorare, meaning 'fish' and 'to devour' respectively.
Sources
[edit]Piscivorin is produced in the venom glands of the Eastern Cottonmouth snake (Agkistrodon piscivorus piscivorus), which populates the Eastern United States.[2] Typically, crude venom from the Eastern Cottonmouth contains approximately 1.25% of piscivorin.[1][3]
Biochemistry
[edit]Piscivorin belongs to the cysteine-rich secretory protein (CRISP) family, which are secreted as single-chain proteins with molecular masses between 20 and 30 kDa. They display significant amino acid sequence homology. Sixteen cysteine residues, forming 8 disulfide bonds, are strictly conserved in CRISPs.[4] Ten of these cysteine residues are clustered into the C-terminal part of the protein.[3]
The molecular mass of piscivorin is 24.842 kDa. The nucleotide sequence of piscivorin cDNA spans 1323 bp, containing an open reading frame of 240 codons.[3]
Piscivorin has the following amino acid sequence.[5]
| 10 | 20 | 30 | 40 | 50 | 60 |
| MIAFIVLPIL | AAVLQQSSGS | VDFDSESPRK | PEIQNQIVDL | HNSLRRSVNP | TASNMLKMEW |
| 70 | 80 | 90 | 100 | 110 | 120 |
| YPEAAANAER | WAYRCIESHS | PRNSRVLGGI | KCGENIYMSS | IPIKWTEIIH | AWHGENKNFK |
| 130 | 140 | 150 | 160 | 170 | 180 |
| YGIGADPPNA | VIGHFTQIVW | YKSYLVGCAA | AYCPSSEYSY | FYVCQYCPAG | NIIGKIATPY |
| 190 | 200 | 210 | 220 | 230 | 240 |
| KSGPPCGDCP | SACVNGLCTN | PCTKEDKYTN | CKSLVQQYGC | QDKQMQSECS | AICFCQNKII |
Target and mode of action
[edit]Piscivorin reduces high potassium-evoked smooth muscle contraction, but does not inhibit caffeine-stimulated contraction of smooth muscle.[3] Since caffeine normally causes contraction through the release of Ca2+ from the sarcoplasmic reticulum, this differential effect indicates that piscivorin is an L-type calcium channel blocker. At a concentration of 1 μM, its effect on depolarization-induced smooth muscle contraction is weaker than of the related CRISP family toxins ablomin, triflin or latisemin. A sequence comparison of piscivorin and other CRISP family proteins suggests that the Glu186 residue is the crucial site for the blocking of the calcium channels.[1][3]
Unlike some other CRISP family proteins, piscivorin does not block cyclic nucleotide-gated channels.[1]
References
[edit] | This article lacks ISBNs for the books listed. (October 2010) |
- ^ a b c d Yamazaki, Yasuo; Hyodo, Fumiko; Morita, Takashi (2003). "Wide distribution of cysteine-rich secretory proteins in snake venoms: Isolation and cloning of novel snake venom cysteine-rich secretory proteins". Archives of Biochemistry and Biophysics. 412 (1): 133–41. doi:10.1016/S0003-9861(03)00028-6. PMID 12646276.
- ^ Campbell, J.A., & Lamar, W. W. (2004). The Venomous Reptiles of the Western Hemisphere. Ithaca and London:Comstock Publishing Associates. Vol. II, p. 271.
- ^ a b c d e Yamazaki, Yasuo; Morita, Takashi (2004). "Structure and function of snake venom cysteine-rich secretory proteins". Toxicon. 44 (3): 227–31. Bibcode:2004Txcn...44..227Y. doi:10.1016/j.toxicon.2004.05.023. PMID 15302528.
- ^ Guo, Min; Teng, Maikun; Niu, Liwen; Liu, Qun; Huang, Qingqiu; Hao, Quan (2004). "Crystal Structure of the Cysteine-rich Secretory Protein Stecrisp Reveals That the Cysteine-rich Domain Has a K+ Channel Inhibitor-like Fold". Journal of Biological Chemistry. 280 (13): 12405–12. doi:10.1074/jbc.M413566200. PMID 15596436.
- ^ "Piscivorin". UniProt Consortium. 2010. Retrieved 27 October 2010.
