title: Structures of Azemiops feae venom phospholipases and cys-rich-secretory protein and implications for taxonomy and toxinology.
abstract: The Azemiops snakes are pit-less and phylogenetically located at the Crotalinae and Viperinae divergence. cDNAs encoding five Azemiops venom phospholipase (sPLA2) molecules were cloned and sequenced; their signal-peptides were similar to those of crotalid sPLA2s. Based on their calculated pI-values and residue-49 substitutions, they were designated as Af-E6, Af-N49a, Af-N49a1, Af-N49a2, and Af-N49b, respectively. The first three isoforms, comprising 3-4% of the venom proteins, were purified by reversed-phase HPLC. Af-E6 is catalytically active and has >80% sequence-similarity to other Glu(6)-PLA2 (a pitviper venom-marker). Results of phylogenetic analyses reveal that acidic Af-N49a and Af-N49a1 are rather unique and loosely linked with crotalid PLA2s, while Af-N49b is related to the viperid PLA2s with Ser(1) substitution. Notably, the Asn(49)-substitutions in these molecules imply catalytic-independent mechanisms. The 3D-models of Af-E6 and Af-N49a have surface electropotential maps similar to each other and to those of antiplatelet PLA2s, while the Af-N49b model is similar to basic and myotoxic sPLA2 molecules. From Azemiops feae and four other Viperidae, we cloned five novel Cys-rich secretory proteins (CRISPs). Azemiops CRISP and natriuretic-peptide precursors share more sequence similarities with those of crotalid venoms than with viperid venoms, further supporting the theory that Azemiops are sister taxons to pit vipers, especially Tropedolaemus.
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan; Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan. Electronic address: bc201@gate.sinica.edu.tw.
authors.forename: Inn-Ho
authors.initials: IH
authors.lastname: Tsai
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan.
authors.forename: Ying-Ming
authors.initials: YM
authors.lastname: Wang
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan.
authors.forename: Kai-Fa
authors.initials: KF
authors.lastname: Huang
mesh_terms: D000818:Animals; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry; D008958:Models, Molecular; D010740:Phospholipases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D030162:Reptilian Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D014757:Viper Venoms / Q000737:chemistry*; D017819:Viperidae / Q000145:classification* / Q000235:genetics / Q000378:metabolism
chemical_list: C049424:Azemiops feae venom; D018076:DNA, Complementary; D030162:Reptilian Proteins; D014757:Viper Venoms; D010740:Phospholipases
keywords: 3D-modeling; Azemiops; Cys-rich secretory protein; Phylogenetic analysis; Viperid venom phospholipase A(2); cDNA cloning and sequencing