Three-dimensional structure of conotoxin tx3a: An m-1 branch peptide of the M-superfamily
Three-dimensional structure of conotoxin tx3a: An m-1 branch peptide of the M-superfamily
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DOI：
10.1021/bi702388b
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发表时间：
2008-03-04
期刊：
影响因子：
2.9
通讯作者：
Poulter, C. Dale
中科院分区：
文献类型：
--
作者：
McDougal, Owen M.;Turner, Matthew W.;Poulter, C. Dale
M-超家族是在芋螺毒液中发现的八个主要芋螺毒素超家族之一，包含具有标记为1、2和3的二硫键连接环的Cys框架（-（CC-C-C-CC）-C-1-C-2-C-3-）。M-超家族芋螺毒素可根据位于第四和第五Cys残基之间的第三Cys环中的残基数目分为m-1、m-2、m-3和m-4分支。在这里，我们提供了一个三维的解决方案结构的m-1芋螺毒素TX 3A中发现的毒液的织锦芋螺。15个氨基酸的肽CCSWDVCDHPSCTCC在Cys和Cys（14）、Cys（2）和Cys（12）以及Cys（7）和Cys（15）之间具有二硫键，这是在m-1分支肽中观察到的典型C1-C5、C2-C4和C3-C6连接模式。利用二维H-1 NMR结合核磁共振（NMR）应用程序CYANA的组合分配和动力学算法确定了tx 3a的三级结构。结构计算的输入包括62个质子间和质子内，5个φ角和4个氢键约束。对于骨架和重原子，20个最终结构的均方根偏差值分别为0.32 +/- 0.07和0.84 +/- 0.11（A）。令人惊讶的是，tx 3a的结构具有在m-2分支芋螺毒素mr 3a中看到的“三转角”基序，其在mr 3e中不存在，mr 3e是其结构已知的M-超家族的m-1分支的唯一其他成员。有趣的是，尽管芋螺毒素具有不同的二硫键连接模式，但将tx 3a注射到小鼠体内引起的兴奋性反应与m-2分支肽mr 3a相似。
The M-superfamily, one of eight major conotoxin superfamilies found in the venom of the cone snail, contains a Cys framework with disulfide-linked loops labeled 1, 2, and 3 (-(CC-C-C-CC)-C-1-C-2-C-3-). M-Superfamily conotoxins can be divided into the m-1, -2, -3, and -4 branches, based upon the number of residues located in the third Cys loop between the fourth and fifth Cys residues. Here we provide a three-dimensional solution structure for the m-1 conotoxin tx3a found in the venom of Conus textile. The 15-amino acid peptide, CCSWDVCDHPSCTCC, has disulfide bonds between Cyst and Cys(14), Cys(2) and Cys(12), and Cys(7) and Cys(15) typical of the C1-C5, C2-C4, and C3-C6 connectivity pattern seen in m-1 branch peptides. The tertiary structure of tx3a was determined by two-dimensional H-1 NMR in combination with the combined assignment and dynamics algorithm for nuclear magnetic resonance (NMR) applications CYANA program. Input for structure calculations consisted of 62 inter- and intraproton, five phi angle, and four hydrogen bond constraints. The root-mean-square deviation values for the 20 final structures are 0.32 +/- 0.07 and 0.84 +/- 0.11 (A) over circle for the backbone and heavy atoms, respectively. Surprisingly, the structure of tx3a has a "triple-turn" motif seen in the m-2 branch conotoxin mr3a, which is absent in mr3e, the only other member of the m-1 branch of the M-superfamily whose structure is known. Interestingly, injection of tx3a into mice elicits an excitatory response similar to that of the m-2 branch peptide mr3a, even though the conotoxins have different disulfide connectivity patterns.