CIRCULAR DICHROIC ANALYSIS OF PROTEIN CONFORMATION - INCLUSION OF BETA-TURNS
CIRCULAR DICHROIC ANALYSIS OF PROTEIN CONFORMATION - INCLUSION OF BETA-TURNS
复制标题
DOI：
10.1016/0003-2697(78)90812-6
复制
发表时间：
1978-01-01
影响因子：
2.9
通讯作者：
YANG, JT
中科院分区：
文献类型：
--
作者：
CHANG, CT;WU, CSC;YANG, JT
水溶液中蛋白质在任何波长λ下的平均残基椭圆率θ表示为θλ。 = fH[.theta.]H.infin.(1 - k/.hivin.n) + f.beta.[.theta.].beta。 + ft[.theta.]t + fR[.theta.]R 有 2 个约束：1 .gtoreq。 fj .gtoreq。 0且.SIGMA.fj = 1。下标H、β、t和R指的是螺旋、β-形式、β-转角和无序形式。 15 种蛋白质的分数 fj 基于 X 射线晶体学。 ft 指的是消除那些具有相反符号的二面角的残基后的净β转角。 .**图形**。无限螺旋的结构及其链长相关因子 k 是根据肌红蛋白数据计算的。 15种蛋白质的残基/螺旋片段的平均数目.hivin.n约为10，这可用于未知结构的蛋白质。其他 3 个结构元素的参考光谱通过最小二乘法计算。选择参考光谱后，可以使用上述相同的方程根据 190-240 nm 之间间隔为 1 nm 的圆二色性数据点来估计蛋白质二级结构的分数。计算出的螺旋含量通常为良好至优秀（伴刀豆球蛋白 A 是一个值得注意的例外）。在分析中包含β-转角提高了β-形式估计值的相关性，但是计算出的β-t值与X射线结果没有显着相关。矩阵公式证明了最小二乘法与积分曲线拟合的等价性。
The mean residue ellipticity, [.theta.], at any wavelength, .lambda., of a protein in aqueous solution is expressed as [.theta.].lambda. = fH[.theta.]H.infin.(1 - k/.hivin.n) + f.beta.[.theta.].beta. + ft[.theta.]t + fR[.theta.]R with 2 constraints: 1 .gtoreq. fj .gtoreq. 0 and .SIGMA.fj = 1. The subscripts H, .beta., t, and R refer to the helix, .beta.-form, .beta.-turn, and unordered form. The fractions, fj, of 15 proteins are based on X-ray crystallography. ft refers to the net .beta.-turn after canceling those residues having dihedral angles of opposite sign. The .**GRAPHIC**. of an infinite helix and its chain-length dependence factor, k, were computed from myoglobin data. The average number of residues/helical segment, .hivin.n, for 15 proteins was about 10, which can be used for proteins of unknown structure. The reference spectra of 3 other structural elements are computed by a least-squares method. Once the reference spectra are chosen, the same equation above can be used to estimate the fractions of the secondary structure of a protein from its circular dichroism data points between 190-240 nm at 1 nm intervals. The computed helical content is usually good to excellent (concanavalin A is a notable exception). Inclusion of the .beta.-turn in the analysis improves the correlation for the estimates of the .beta.-form, but the computed .beta.t values are not significantly correlated with the X-ray results. Matrix formulation proves the equivalence of the least-squares method and the integral curve-fitting.