THE ENERGETICS OF ION-PAIR AND HYDROGEN-BONDING INTERACTIONS IN A HELICAL PEPTIDE
THE ENERGETICS OF ION-PAIR AND HYDROGEN-BONDING INTERACTIONS IN A HELICAL PEPTIDE
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DOI：
10.1021/bi00088a019
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发表时间：
1993-09-21
期刊：
影响因子：
2.9
通讯作者：
BALDWIN, RL
中科院分区：
文献类型：
--
作者：
SCHOLTZ, JM;QIAN, H;BALDWIN, RL
在中性的丙氨酸-谷氨酰胺肽螺旋中，一对 Glu 和 Lys 残基以四种不同的间距和两个方向放置，并且测量了不同 Glu-Lys 相互作用对螺旋稳定性的贡献。每个带电侧链与螺旋巨偶极子相互作用的贡献也已确定。当间距为 (i, i+4) 时，已检测到并量化了 Gln 和 Glu 之间的侧链相互作用。相互作用分为氢键作用（与 NaCl 浓度无关）和静电相互作用（存在于 10 mM NaCl 中，不存在于 2.5 M NaCl 中）。主要结果如下：（1）（i，i+3）和（i，i+4）Glu-Lys相互作用是螺旋稳定的，并且无论侧链的方向如何，强度彼此相似。 (2) 氢键对这些侧链相互作用做出了主要贡献，如下事实所示。首先，在 10 mM 氯化钠（pH 7）中观察到的相互作用的主要部分仍然存在于 2.5 M 氯化钠中。其次，在 pH 2 下发现的相互作用与在 pH 7 下的 2.5 M 氯化钠中发现的相互作用同样强。 (3) 在 pH 2 和 pH 7 下，(i, i+4) Gln-Glu 侧链氢键与 Glu-Lys 相互作用的氢键成分一样强。Gln-Glu 相互作用与 Glu-Lys 相互作用的不同之处在于残基的方向和间距都具有特异性。 (4) 在 2.5 M NaCl 中，在 pH 2 或 pH 7 下，(i,i+1) 或 (i, i+2) Glu-Lys 间距没有发现显着的氢键相互作用。在 10 mM NaCl 和 pH 7 下，这些间距显示出螺旋不稳定的静电相互作用，这可能是由于线圈构象的稳定造成的。
A single pair of Glu and Lys residues has been placed at four different spacings, and in both orientations, in an otherwise neutral alanine-glutamine peptide helix, and the contribution to helix stability of the different Glu-Lys interactions has been measured. The contribution from the interaction of each charged side chain with the helix macrodipole has also been determined. A side-chain interaction between Gln and Glu, when the spacing is (i, i+4), has been detected and quantified. The interactions have been divided into contributions from hydrogen bonds (independent of the concentration of NaCl) and from electrostatic interactions (present in 10 mM NaCl, absent in 2.5 M NaCl). The major results are as follows: (1) The (i, i+3) and (i, i+4) Glu-Lys interactions are helix-stabilizing and are similar in strength to each other, regardless of the orientation of the side chains. (2) Hydrogen bonds provide the major contribution to these side-chain interactions, as shown by the following facts. First, the major part of the interaction observed in 10 mM NaCl, pH 7, is still present in 2.5 M NaCl. Second, the interaction found at pH 2 is equally as strong as that found in 2.5 M NaCl at pH 7. (3) The (i, i+4) Gln-Glu side-chain hydrogen bond is as strong as the hydrogen-bond component of the Glu-Lys interaction at both pH 2 and pH 7. The Gln-Glu interaction differs from the Glu-Lys interaction in being specific both for the orientation and the spacing of the residues. (4) No significant hydrogen-bonding interaction was found for the (i,i+1) or (i, i+2) Glu-Lys spacings, either at pH 2 or at pH 7, in 2.5 M NaCl. At 10 mM NaCl and pH 7, these spacings show a helix-destabilizing electrostatic interaction which probably results from stabilization of the coil conformation.