cDNA Cloning and Deduced Amino Acid Sequence of Prothrombin Activator (Ecarin) from Kenyan Echis carinatus Venom

Shinji Nishida, Taizo Fujita, Noriatsu Kohno, Hideko Atoda, Takashi Morita, Hiroyuki Takeya, Isao Kido, Mark J.I. Paine, Shun-Ichiro Kawabata, Sadaaki Iwanaga

Research output: Contribution to journalArticlepeer-review

80 Citations (Scopus)

Abstract

The complete amino acid sequence of ecarin is deduced from the nucleotide sequence of a cDNA clone isolated by screening a venomous gland cDNA library of Kenyan Echis carinatus. The cDNA sequence with 2379 base pairs encodes an open reading frame of 616 amino acids with a remarkable sequence homology to the putative precursor protein of trigramin from Trimeresurus gramineus venom (61% identity) and a large hemorrhagin, jararhagin, from the pit viper Bothrops jararaca venom (62% identity). Thus, ecarin, as well as jararhagin and trigramin, is translated as a precursor protein, which may be processed posttranslationally. The ecarin proprotein has a “cysteine switch” motif (-Pro-Lys- Met-Cys-Gly-Val-) similar to that involved in the activation of matrix metalloproteinase zymogens. The processed mature protein consists of 426 amino acid residues (residues 191-616), showing the strongest sequence similarity with that of Russell's viper venom factor X activator (RVV-X) heavy chain (64% identity). Like RVV-X heavy chain, ecarin contains metalloproteinase, disintegrin, and cysteine-rich domains. The metalloproteinase domain has a typical zinc-chelating sequence (-His-Glu-Xaa-Xaa-His- Xaa-Xaa-Gly-Xaa-Xaa-His-), as found in crayfish astacin. In the disintegrin domain of ecarin, the Arg- Gly-Asp sequence is replaced by Arg-Asp-Asp, as found in the disintegrin domains of RVV-X heavy chain (Arg-Asp-Glu) and a guinea pig sperm fusion protein, PH-30β (Thr-Asp-Glu). These findings show that while there are structural and evolutionary relationships among these proteins, each has a unique functional activity.

Original languageEnglish
Pages (from-to)1771-1778
Number of pages8
JournalBiochemistry
Volume34
Issue number5
DOIs
Publication statusPublished - Jan 1 1995

All Science Journal Classification (ASJC) codes

  • Biochemistry

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