title: Comparative analysis of prothrombin activators from the venom of Australian elapids.
abstract: A key component of the venom of many Australian snakes belonging to the elapid family is a toxin that is structurally and functionally similar to that of the mammalian prothrombinase complex. In mammals, this complex is responsible for the cleavage of prothrombin to thrombin and is composed of factor Xa in association with its cofactors calcium, phospholipids, and factor Va. The snake prothrombin activators have been classified on the basis of their requirement for cofactors for activity. The two major subgroups described in Australian elapid snakes, groups C and D, are differentiated by their requirement for mammalian coagulation factor Va. In this study, we describe the cloning, characterization, and comparative analysis of the factor X- and factor V-like components of the prothrombin activators from the venom glands of snakes possessing either group C or D prothrombin activators. The overall domain arrangement in these proteins was highly conserved between all elapids and with the corresponding mammalian clotting factors. The deduced protein sequence for the factor X-like protease precursor, identified in elapids containing either group C or D prothrombin activators, demonstrated a remarkable degree of relatedness to each other (80%-97%). The factor V-like component of the prothrombin activator, present only in snakes containing group C complexes, also showed a very high degree of homology (96%-98%). Expression of both the factor X- and factor V-like proteins determined by immunoblotting provided an additional means of separating these two groups at the molecular level. The molecular phylogenetic analysis described here represents a new approach for distinguishing group C and D snake prothrombin activators and correlates well with previous classifications.
authors.affiliation: The Queensland Cancer Fund Research Unit, The Queensland Institute of Medical Research, Royal Brisbane Hospital, Brisbane, Australia.
authors.forename: Liam
authors.initials: L
authors.lastname: St Pierre
authors.forename: Paul P
authors.initials: PP
authors.lastname: Masci
authors.forename: Igor
authors.initials: I
authors.lastname: Filippovich
authors.forename: Natasha
authors.initials: N
authors.lastname: Sorokina
authors.forename: Neville
authors.initials: N
authors.lastname: Marsh
authors.forename: David J
authors.initials: DJ
authors.lastname: Miller
authors.forename: Martin F
authors.initials: MF
authors.lastname: Lavin
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001315:Australia; D018076:DNA, Complementary; D004546:Elapid Venoms / Q000737:chemistry / Q000494:pharmacology*; D017815:Elapidae / Q000145:classification / Q000235:genetics*; D004789:Enzyme Activation; D015943:Factor Va / Q000235:genetics* / Q000302:isolation & purification; D015951:Factor Xa / Q000235:genetics* / Q000302:isolation & purification; D005784:Gene Amplification; D008969:Molecular Sequence Data; D010802:Phylogeny; D011516:Prothrombin / Q000235:genetics* / Q000378:metabolism; D011517:Prothrombin Time; D016415:Sequence Alignment
chemical_list: D018076:DNA, Complementary; D004546:Elapid Venoms; D015943:Factor Va; D011516:Prothrombin; D015951:Factor Xa