3-DIMENSIONAL STRUCTURE IN SOLUTION OF THE POLYPEPTIDE CARDIAC STIMULANT ANTHOPLEURIN-A
3-DIMENSIONAL STRUCTURE IN SOLUTION OF THE POLYPEPTIDE CARDIAC STIMULANT ANTHOPLEURIN-A
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DOI：
10.1021/bi00011a036
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发表时间：
1995-03-21
期刊：
影响因子：
2.9
通讯作者：
NORTON, RS
中科院分区：
文献类型：
--
作者：
PALLAGHY, PK;SCANLON, MJ;NORTON, RS
用核磁共振氢谱测定了海葵Anthopleura xanthogramica的49个氨基酸的多肽anthopleurin-A（AP-A）在水溶液中的三维结构。一个约束组包括411个质子间距离约束推断NOE和19个骨干和13个侧链二面角限制自旋-自旋耦合常数，以及15个下限约束的基础上没有NOE的光谱，被用作输入的距离几何计算DIANA和模拟退火和约束能量最小化的X-PLOR。还包括12个β-亚甲基对的立体特异性分配。最后一组20个结构在整个分子上的平均成对rms差对于骨架重原子（N、C-alpha和C）为2.04埃，对于所有重原子为2.59埃。对于包括残基2-7和17-49的明确限定的区域，相应的值分别为0.82和1.27埃。AP-A采用由三个环连接的反平行β-折叠的四条短链（残基2-4、20-23、34-37和45-48）组成的紧凑结构。第一个环以I型β转角开始，其中包括两个重要的Asp残基;该环是蛋白质的最不明确的区域，尽管在近一半的结构中观察到涉及残基13-16的β转角。连接第二条和第三条链的环受到29-47二硫键的限制，并含有两个明确的β-转角，而第三环含有Gly 40-Pro41序列，该序列先前已被鉴定为顺反异构位点。Asp 7的羧酸基团接近Lys 37的ε-铵基团，表明它们可能形成盐桥。通过2D NMR监测的pH滴定通过显示Asp 7具有低pK（a）来支持这一点。有人提出，该区域的分子和附近的残基Asp 9和His 39形成的分子表面的一部分，与哺乳动物心脏钠通道相互作用。
The three-dimensional structure in aqueous solution of the 49-residue polypeptide anthopleurin-A (AP-A), from the sea anemone Anthopleura xanthogramica, has been determined from H-1 NMR data. A restraint set consisting of 411 interproton distance restraints inferred from NOEs and 19 backbone and 13 side chain dihedral angle restraints from spin-spin coupling constants, as well as 15 lower bound restraints based on the absence of NOEs in the spectra, was used as input for distance geometry calculations in DIANA and simulated annealing and restrained energy minimization in X-PLOR. Stereospecific assignments for 12 beta-methylene pairs were also included. The final set of 20 structures had mean pairwise rms differences over the whole molecule of 2.04 Angstrom for the backbone heavy atoms (N, C-alpha, and C) and 2.59 Angstrom for all heavy atoms. For the well-defined region encompassing residues 2-7 and 17-49, the corresponding values were 0.82 and 1.27 Angstrom, respectively. AP-A adopts a compact structure consisting of four short strands of antiparallel beta-sheet (residues 2-4, 20-23, 34-37, and 45-48) connected by three loops. The first loop commences with a type I beta-turn which includes two important Asp residues; this loop is the least well-defined region of the protein, although a beta-turn involving residues 13-16 is observed in nearly half the structures. The loop linking the second and third strands is constrained by the 29-47 disulfide bond and contains two well-defined beta-turns, while the third loop contains the Gly40-Pro41 sequence, which has been identifed previously as the site of cis-trans isomerism. The carboxylate group of Asp7 is close to the epsilon-ammonium group of Lys37, suggesting that they may form a salt bridge. A pH titration monitored by 2D NMR supports this by showing that Asp7 has a low pK(a). It is proposed that this region of the molecule and the nearby residues Asp9 and His39 form part of the molecular surface which interacts with the mammalian cardiac sodium channel.