THE NMR STRUCTURE OF THE PULMONARY SURFACTANT-ASSOCIATED POLYPEPTIDE SP-C IN AN APOLAR SOLVENT CONTAINS A VALYL-RICH ALPHA-HELIX
THE NMR STRUCTURE OF THE PULMONARY SURFACTANT-ASSOCIATED POLYPEPTIDE SP-C IN AN APOLAR SOLVENT CONTAINS A VALYL-RICH ALPHA-HELIX
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DOI：
10.1021/bi00185a042
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发表时间：
1994-05-17
期刊：
影响因子：
2.9
通讯作者：
WUTHRICH, K
中科院分区：
文献类型：
--
作者：
JOHANSSON, J;SZYPERSKI, T;WUTHRICH, K
在（CH_3Cl）-H-2/（CH_3OH）-H-2/0.1M HCl 32：64：5（v/v）混合溶剂中测定了肺表面活性物质相关脂多肽C（SP-C）的核磁共振（NMR）结构。序列特异性H-1 NMR归属和构象约束的收集用二维H-1 NMR实现，并且结构用距离几何程序DIANA计算，对于20个最佳能量-浓度计算的残基9-34的明确定义的多肽区段的均方根偏差。对于多肽骨架原子N、C-α和C ′，以及对于所有重原子，最小化的DIANA构象异构体相对于它们的平均值分别为0.5和1.3埃。SP-C的35个残基的多肽链在位置9和34之间形成Lu-螺旋，其包括由单个亮氨酰残基分开的七个和四个连续的谷氨酰的两个区段。N-末端六肽段，其中包括两个棕榈酰半胱氨酰，灵活无序。α-螺旋的长度为约37埃，残基13-28的螺旋片段（其仅包含具有分支侧链的脂族残基）为23埃长，直径为约10埃。α-螺旋非常规则，所有缬氨酰残基的卡方角几乎相同。SP-C的螺旋结构的观察是相当出乎意料的，考虑到瓦尔通常在α-螺旋中代表性不足，并且它提供了对SP-C功能的结构基础以及生物膜中蛋白质-脂质相互作用的一般结构方面的有趣的新见解。
The nuclear magnetic resonance (NMR) structure of the pulmonary surfactant-associated lipopolypeptide C (SP-C) was determined in a mixed solvent of (CH3Cl)-H-2/(CH3OH)-H-2/0.1 M HCl 32:64:5 (v/v). Sequence-specific H-1 NMR assignments and the collection of conformational constraints were achieved with two-dimensional H-1 NMR, and the structure was calculated with the distance geometry program DIANA, The root mean square deviations for the well-defined polypeptide segment of residues 9-34 calculated for the 20 best energy-minimized DIANA conformers relative to their mean are 0.5 and 1.3 Angstrom for the polypeptide backbone atoms N, C-alpha, and C', and for all heavy atoms, respectively. The 35-residue polypeptide chain of SP-C forms an Lu-helix between positions 9 and 34, which includes two segments of seven and four consecutive valyls that are separated by a single leucyl residue. The N-terminal hexapeptide segment, which includes two palmitoylcysteinyls, is flexibly disordered. The length of the alpha-helix is about 37 Angstrom, and the helical segment of residues 13-28, which contains exclusively aliphatic residues with branched side chains, is 23-Angstrom long and about 10 Angstrom in diameter. The alpha-helix is outstandingly regular, with virtually identical chi(1) angles for all valyl residues. The observation of a helical structure of SP-C was rather unexpected, considering that Val is generally underrepresented in alpha-helices, and it provides intriguing novel insights into the structural basis of SP-C functions as well as into general structural aspects of protein-lipid interactions in biological membranes.