Structure and function of a new endothelial growth factor from snake venom

肝素结合二聚体降压因子(HF)是从毒蛇蛇毒[Komori，Y.和Sugihara，H.(1990)Toxicon 28,359-369]中分离得到的。本研究对HF的氨基酸序列、结构和功能进行了阐述。经电喷雾电离质谱仪(ESI-MS)测定，HF的相对分子质量为25072.1。用Edman测序法测定了S-吡啶乙基化氢酶及其酶解多肽的氨基酸序列。由一级结构计算的理论相对分子质量与ESI-MS测定的相对分子质量吻合较好。氢氟酸由两个共价结合的均相单体组成。N-末端被焦谷氨酸封闭的单体含有110个氨基酸残基，其中8个半胱氨酸残基，其中2个被认为参与了分子间二硫键。序列同源性搜索发现，HF的一级结构与血管内皮生长因子(VEGF)和血小板衍生生长因子(PDGF)相似，序列同源性分别为45%和22%。大鼠皮内注射HF或VEGF后，毛细血管通透性增加。大鼠静脉注射HF后，只有HF有较强的降压作用。纯化的HF对内皮细胞具有促有丝分裂作用。用牛主动脉内皮细胞(BAEC)测得HF的半数有丝分裂浓度为5-5.5 nM(125-138 ng/ml)。同样，血管内皮细胞生长因子在0.5-1 nM有丝分裂浓度。当HF与放线菌酮或HF与肝素共同孵育时，细胞生长受到抑制，提示HF的作用机制与血管内皮细胞生长因子相似。

The heparin-binding dimeric hypotensive factor (HF) was purified from Vipera aspis aspis (Aspic viper) venom [Komori, Y. and Sugihara, H. (1990) Toxicon 28, 359-369]. In this study, the amino acid sequence, and structure and function of HF were elucidated. By electrospray ionization mass spectrometry (ESI-MS), the molecular weight of HF was determined to be 25,072.1. The complete amino acid sequence of HF was determined by Edman sequencing of the S-pyridylethylated HF and its peptides derived from enzymatic digestion. The theoretical molecular mass calculated from the primary structure agrees well with the molecular weight determined by ESI-MS. HF consists of two homogenous monomers bound covalently. The monomer with an N-terminal blocked by pyro-glutamic acid contains 110 amino acid residues including 8 cysteine residues, 2 of which are considered to be involved in intermolecular disulfide bonds. Sequential homology search revealed that the primary structure of HF is similar to that of vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) with a sequential homology of 45% and 22%, respectively. When injected intradermally into rat, an increase in capillary permeability was observed with HF or VEGF. On the other hand, only HF exerted a strong hypotensive effect immediately after intravenous injection into rat. Purified HF has a mitogenic effect on endothelial cells. Using bovine aortic endothelial cells (BAEC), the half maximal mitogenic concentration of HF was determined to be 5-5.5 nM (125-138 ng/ml). Similarly, VEGF had a mitogenic concentration at 0.5-1 nM. When incubated with HF and cycloheximide or HF and heparin, the cell growth was inhibited, suggesting that the mechanism of action of HF is similar to that of VEGF.