Tsai Inn-Ho, Wang Ying-Ming, Huang Kai-Fa
Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan; Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan.
Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan.
Toxicon. 2016 May;114:31-9. doi: 10.1016/j.toxicon.2016.02.014. Epub 2016 Feb 18.
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.
白头蝰蛇没有颊窝，在系统发育上位于蝰亚科和蝮亚科的分化位置。克隆并测序了编码五种白头蝰蛇毒磷脂酶（sPLA2）分子的cDNA；它们的信号肽与蝰蛇科sPLA2的信号肽相似。根据它们计算出的pI值和第49位残基的替换情况，它们分别被命名为Af-E6、Af-N49a、Af-N49a1、Af-N49a2和Af-N49b。前三种异构体占毒液蛋白的3-4%，通过反相高效液相色谱法进行纯化。Af-E6具有催化活性，与其他Glu(6)-PLA2（一种蝮蛇毒标记物）的序列相似性>80%。系统发育分析结果表明，酸性的Af-N49a和Af-N49a1相当独特，与蝰蛇科PLA2的联系较为松散，而Af-N49b与具有Ser(1)替换的蝰蛇科PLA2相关。值得注意的是，这些分子中的Asn(49)替换意味着非催化机制。Af-E6和Af-N49a的三维模型具有彼此相似且与抗血小板PLA2相似的表面电势图，而Af-N49b模型与碱性和肌毒性sPLA2分子相似。从白头蝰和其他四种蝰蛇科动物中，我们克隆了五种新的富含半胱氨酸的分泌蛋白（CRISPs）。白头蝰CRISP和利钠肽前体与蝰蛇科毒液的序列相似性比与蝰蛇科毒液的序列相似性更高，进一步支持了白头蝰是蝮蛇的姐妹分类群，尤其是竹叶青属的理论。
