Experimental investigation of initial steps of helix propagation in model peptides
Experimental investigation of initial steps of helix propagation in model peptides
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DOI：
10.1021/bi027339d
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发表时间：
2003-06-10
期刊：
影响因子：
2.9
通讯作者：
Bierzynski, A
中科院分区：
文献类型：
--
作者：
Goch, G;Maciejczyk, M;Bierzynski, A
不确定螺旋传播参数s（n）（即，从相当长的模型肽的大量研究中确定的（N - 1）-和N-残基长α-螺旋之间的平衡常数适用于描述蛋白质折叠过程中螺旋形成的初始步骤。根据对一系列模型肽的荧光、NMR和量热研究，所述模型肽含有使螺旋成核的La 3+结合序列（Siedlecka，M.，Goch，G.，埃查特，A.，Sticht，H.，和Bierzynski，A.等人（1999）Proc. Acad. Sci. U.S.A.96，903-908），我们在25 ℃下测定了描述聚丙氨酸中螺旋增长的前四步的焓Δ H（n）和螺旋生长参数s（n）的平均值。还估计了丙氨酸（1.2 +/- 0.5）和NH 2基团（1.6 +/- 0.7）的C-帽参数的绝对值，描述了C-末端残基对螺旋自由能的贡献。聚丙氨酸中螺旋生长的最初四个步骤可以通过共同的传播参数s = 1.54 +/- 0.04来描述。焓Δ H（n）也是常数，等于-980 +/-100 cal mol（-1）。
It is not certain whether the helix propagation parameters s(n) (i.e., the equilibrium constants between (n - 1)- and n-residue long alpha-helices) determined from numerous studies of rather long model peptides are applicable for description of the initial steps of the helix formation during the protein folding process. From fluorescence, NMR, and calorimetric studies of a series of model peptides, containing the La3+-binding sequence nucleating the helix (Siedlecka, M., Goch, G., Ejchart, A., Sticht, H., and Bierzynski, A. (1999) Proc. Natl. Acad. Sci. U.S.A. 96, 903-908), we have determined, at 25 degreesC, the average values of the enthalpy DeltaH(n) and of the helix growth parameters s(n) describing the first four steps of helix propagation in polyalanine. The absolute values of the C-cap parameters, describing the contribution of the C-terminal residues to the helix free energy, have also been estimated for alanine (1.2 +/- 0.5) and NH2 group (1.6 +/- 0.7). The initial four steps of the helix growth in polyalanine can be described by a common propagation parameter s = 1.54 +/- 0.04. The enthalpy DeltaH(n) is also constant and equals -980 +/- 100 cal mol(-1).