【摘要】 此前,我们曾报道过一种新的蛇毒肽(缓激肽加强肽,缩写为BIP),其在离体豚鼠回肠和大鼠胃底肌条上表现了不同的生理活性。为了探索它与其它缓激肽增强肽在生物活性上不同的原因,本文运用2D NMR技术研究了其在水溶液中的构象,利用RMSD和Ramachandran plot分析结果的可靠性。结果表明,Pro2、Pro3、Pro6和Pro10的肽键都处于反式构象,整体结构呈现"双S"形状,N-端(Pro2Pro3Ala4)形成新生螺旋,C-端(Asp7Val8Gly9Pro10)形成Ⅱ型β-转角。与其它缓激肽抑制剂(如HOE140)相比较,C-端的Ⅱ型β-转角在维持缓激肽抑制活性方面起到关键作用;而N端的新生螺旋结构可能与缓激肽加强活性有关。更多还原

【Abstract】 Previously,we reported the dual bio-activities of a novel snake venom peptide(BIP) on isolated guinea pig ileum(GPI) and rat stomach fundus.It observably inhibits bradykinin’s contractivity on GPI,but potentiates the bradykinin-induced contractivity on rat stomach fundus.To explore what the difference is between BIP and other bradykinin potentiating peptides,its conformation was studied by 2D NMR spectroscopy in water.RMSD and Ramachandran plot were analyzed.Results show that,the peptide bonds in Pro2,Pro3,Pro6 and Pro10 are all in trans conformations;the whole structure of BIP forms a "double-S" like conformation;N-terminal has a nascent helix(Pro2Pro3Ala4);C-terminal has an invariant type II β-turn(Asp7Val8Gly9Pro10) which is critical for binding with B2 receptor.According to the same structures of HOE140 and other bradykinin antagonists at C-terminal,the C-terminal highly invariant β-turn structure shows the BIP properties;the N-terminal nascent helix may be related to bradykinin-potentiating peptides’ properties.更多还原