Newcomb R, Palma A, Fox J, Gaur S, Lau K, Chung D, Cong R, Bell J R, Horne B, Nadasdi L
Neurex Corporation, Menlo Park, California 94025-1012, USA.
Biochemistry. 1995 Jul 4;34(26):8341-7. doi: 10.1021/bi00026a015.
A novel selective calcium channel antagonist peptide, SNX-325, has been isolated from the venom of the spider Segestria florentina. The peptide was isolated using as bioassays the displacement of radioiodinated omega-conopeptide SNX-230 (MVIIC) from rat brain synaptosomal membranes, as well as the inhibition of the barium current through cloned expressed calcium channels in oocytes. The primary sequence of SNX-325 is GSCIESGKSCTHSRSMKNGLCCPKSRCNCRQIQHRHDYLGKRKYSCRCS, which is a novel amino acid sequence. Solid-phase synthesis resulted in a peptide that is chromatographically identical with the native peptide and which has the same configuration of cysteine residues as the spider venom peptide omega-Aga-IVa [Mintz, I. M., et al., (1992) Nature 355, 827-829]. At micromolar concentrations, SNX-325 is an inhibitor of most calcium, but not sodium or potassium, currents. At nanomolar concentrations, SNX-325 is a selective blocker of the cloned expressed class B (N-type), but not class C (cardiac L), A, or E, calcium channels. SNX-325 is approximately equipotent with the N-channel selective omega-conopeptides (GVIA and MVIIA as well as closely related synthetic derivatives) in blocking the potassium induced release of tritiated norepinephrine from hippocampal slices (IC50s, 0.1-0.5 nM) and in blocking the barium current through cloned expressed N-channels in oocytes (IC50s 3-30 nM). By contrast, SNX-325 is 4-5 orders of magnitude less potent than is SNX-111 (synthetic MVIIA) at displacing radioiodinated SNX-111 from rat brain synaptosomal membranes. SNX-325 will be a useful comparative tool in further defining the function and pharmacology of the N- and possibly other types of high-voltage activated calcium channels.
一种新型选择性钙通道拮抗剂肽SNX - 325已从蜘蛛佛罗伦萨塞格斯特里蛛的毒液中分离出来。该肽的分离采用了放射性碘化ω -芋螺毒素SNX - 230（MVIIC）从大鼠脑突触体膜上的置换作为生物测定方法，以及通过卵母细胞中克隆表达的钙通道对钡电流的抑制作用。SNX - 325的一级序列为GSCIESGKSCTHSRSMKNGLCCPKSRCNCRQIQHRHDYLGKRKYSCRCS，这是一个新的氨基酸序列。固相合成得到的肽在色谱上与天然肽相同，并且其半胱氨酸残基的构型与蜘蛛毒液肽ω - Aga - IVa相同[明茨，I. M.等人，（1992年）《自然》355卷，827 - 829页]。在微摩尔浓度下，SNX - 325是大多数钙电流的抑制剂，但不是钠电流或钾电流的抑制剂。在纳摩尔浓度下，SNX - 325是克隆表达的B类（N型）钙通道的选择性阻滞剂，但不是C类（心脏L型）、A类或E类钙通道的阻滞剂。在阻断海马切片中钾诱导的氚化去甲肾上腺素释放（IC50为0.1 - 0.5 nM）以及阻断卵母细胞中克隆表达的N型通道的钡电流（IC50为3 - 30 nM）方面，SNX - 325与N通道选择性ω -芋螺毒素（GVIA和MVIIA以及密切相关的合成衍生物）效力大致相当。相比之下，在从大鼠脑突触体膜上置换放射性碘化SNX - 111方面，SNX - 325的效力比SNX - 111（合成MVIIA）低4 - 5个数量级。SNX - 325将成为进一步明确N型以及可能其他类型的高电压激活钙通道的功能和药理学的有用比较工具。
