Nature and locations of the most slowly exchanging peptide NH protons in residues 1 to 19 of ribonuclease S.
Nature and locations of the most slowly exchanging peptide NH protons in residues 1 to 19 of ribonuclease S.
复制标题
核糖核酸酶 S 残基 1 至 19 中最慢交换肽 NH 质子的性质和位置。
DOI：
10.1016/s0022-2836(83)80184-3
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发表时间：
1983
影响因子：
5.6
通讯作者：
Baldwin,RL
中科院分区：
文献类型：
--
作者：
Kuwajima,K;Baldwin,RL
已发现核糖核酸酶 S 的残基 1 至 19 中交换速度最慢的 8 个肽质子的位置。当 S 肽（残基 1 至 19）或肽 1-15 与 S 蛋白（残基 21 至 124）结合时，通过 360 MHz 的质子磁共振解析这 8 个质子的共振线。其他肽质子已通过样品制备中的交换（[1H]S-肽添加到 D2O 中的氘化 S-蛋白中）以及残基 1 至 19 中受保护较少的质子的交换而被去除。在 pH 5·1、0°C 下，S 肽的 8 个受保护程度最高的质子与受保护程度较低的质子之间的交换率存在 100 倍的差异。与游离 S 肽相比，高度保护的质子受到的保护是 104 倍。在 ≥3m-urea-d4、D2O、pH 2·3、-4°C 中使核糖核酸酶 S 变性后，通过 1H 核磁共振鉴定出受保护的质子，然后将其余 8 个质子的化学位移与已知的游离肽的 -NH 谱进行比较，该谱是从二维同核相关谱中分配的，并与早期工作进行比较。这 8 个高度保护的 NH 质子位于一个片段中，残基7至14。所有八个质子都是氢键合：残基7至13的质子在3-13 α-螺旋内氢键合，残基14的质子与β-折叠氢键合。残基 16 的 NH 质子也与 β-折叠形成氢键，不是高度保护的质子之一。根据 Finney (1978) 的分子面积计算，在大多数情况下，八个 NH 基团的 N 原子及其 CO 受体基团的 O 原子都与溶剂隔离。
The locations have been found of the eight most slowly exchanging peptide protons in residues 1 to 19 of ribonuclease S. The resonance lines of these eight protons are resolved by proton magnetic resonance at 360 MHz when either S-peptide (residues 1 to 19) or peptide 1-15 is bound to S-protein (residues 21 to 124). Other peptide protons have been removed by exchange in the sample preparation ([1H]S-peptide is added to deuterated S-protein in D2O), and also by exchange-out of the less protected protons in residues 1 to 19.At pH 5·1, 0°C, there is a 100-fold difference in rates of exchange between the eight most protected protons and the less protected protons of S-peptide. The highly protected protons are protected 104-fold compared to free S-peptide. The protected protons have been identified by1H nuclear magnetic resonance after denaturing ribonuclease S in ≥3m-urea-d4, D2O, pH 2·3, −4°C, followed by comparing the chemical shifts of the remaining eight protons with the known -NH spectrum of the free peptide, which has been assigned from the two-dimensional homonuclear correlated spectrum and by comparison with earlier work.The eight highly protected NH protons are localized in one segment, residues 7 to 14. All eight protons are H-bonded: those of residues 7 to 13 are H-bonded within the 3-13 α-helix and that of residue 14 is H-bonded to the β-sheet. The NH proton of residue 16, which also is H-bonded to the β-sheet, is not one of the highly protected protons. Both the N atoms of the eight NH groups and also the O atoms of their CO acceptor groups are shielded from solvent in most cases, according to the molecular area calculations of Finney (1978).