Falkenstein R J, Peña C
Instituto de Química y Fisicoquímica Biológicas, Departamento de Química Biológica, Facultad de Farmacia y Bioquímica, Universidad deBuenos Aires, Argentina.
Biochim Biophys Acta. 1997 Jun 20;1340(1):143-51. doi: 10.1016/s0167-4838(97)00040-x.
Fasciculins are peptides present in the venom of green and black mamba snakes, with potent inhibitory activity towards acetylcholinesterase. In order to determine the role of fasciculin loop II in the acetylcholinesterase inhibition, two fasciculin fragments were synthesized by the solid phase procedure using N-alpha-Boc protected amino acids. The two peptides, Fas-A and Fas-B, span the 26-32 and 22-35 sequences of fasciculin and a disulfide bridge links each peptide end, thus ensuring the formation of a looped structure. Both peptides were characterized chemically, structurally and functionally. Circular dichroism indicated the existence of 19.4 and 24.9% of beta-sheet for Fas-A and Fas-B, respectively; SDS-PAGE patterns and mass spectrometry disclosed the intramolecular disulfide formation in both peptides. An inhibitory effect on eel acetylcholinesterase was observed with the longer peptide (Ki = 15.1 microM), without reaching the affinity level of the parent native toxin (Ki = 0.3 nM). This study confirms that fasciculin central loop residues strongly contribute to toxin interaction with acetylcholinesterase.
束丝菌素是存在于绿曼巴蛇和黑曼巴蛇毒液中的肽类，对乙酰胆碱酯酶具有强大的抑制活性。为了确定束丝菌素环II在乙酰胆碱酯酶抑制中的作用，使用N-α-叔丁氧羰基保护的氨基酸通过固相方法合成了两个束丝菌素片段。这两个肽，Fas-A和Fas-B，跨越束丝菌素的26-32和22-35序列，并且一个二硫键连接每个肽的末端，从而确保形成环状结构。对这两个肽进行了化学、结构和功能表征。圆二色性表明Fas-A和Fas-B分别存在19.4%和24.9%的β-折叠；SDS-PAGE图谱和质谱显示两种肽中均形成了分子内二硫键。观察到较长的肽对鳗鱼乙酰胆碱酯酶有抑制作用（Ki = 15.1 microM），但未达到亲本天然毒素的亲和力水平（Ki = 0.3 nM）。这项研究证实束丝菌素的中央环残基对毒素与乙酰胆碱酯酶的相互作用有很大贡献。
