title: Convergent evolution of novel protein function in shrew and lizard venom.
abstract: How do proteins evolve novel functions? To address this question, we are studying the evolution of a mammalian toxin, the serine protease BLTX [1], from the salivary glands of the North American shrew Blarina brevicauda. Here, we examine the molecular changes responsible for promoting BLTX toxicity. First, we show that regulatory loops surrounding the BLTX active site have evolved adaptively via acquisition of small insertions and subsequent accelerated sequence evolution. Second, these mutations introduce a novel chemical environment into the catalytic cleft of BLTX. Third, molecular-dynamic simulations show that the observed changes create a novel chemical and physical topology consistent with increased enzyme catalysis. Finally, we show that a toxic serine protease from the Mexican beaded lizard (GTX) [2] has evolved convergently through almost identical functional changes. Together, these results suggest that the evolution of toxicity might be predictable-arising via adaptive structural modification of analogous labile regulatory loops of an ancestral serine protease-and thus might aid in the identification of other toxic proteins.
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Yael T
authors.initials: YT
authors.lastname: Aminetzach
authors.forename: John R
authors.initials: JR
authors.lastname: Srouji
authors.forename: Chung Yin
authors.initials: CY
authors.lastname: Kong
authors.forename: Hopi E
authors.initials: HE
authors.lastname: Hoekstra
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D055162:Biocatalysis; D008116:Lizards; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D012788:Shrews; D014688:Venoms / Q000737:chemistry / Q000235:genetics* / Q000633:toxicity
chemical_list: D014688:Venoms