Hirudin is
(1) a protein produced by Hordeum vulgare, which is rich in lysine
(2) a toxic molecule isolated from Gossypium hirsutum, which reduces human fertility
(3) a protein produced from transgenic Brassica napus, which prevents blood clotting
(4) an antibiotic produced by a genetically enginnered bacterium, Escherichia coli
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