Maciejewski M W, Zehfus M H
Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, Ohio State University, Columbus 43210, USA.
Biochemistry. 1995 May 2;34(17):5795-800. doi: 10.1021/bi00017a010.
Compact regions in proteins are thought to correspond to domains. If this is true, the structure of a compact region excised from a protein should closely resemble the structure in the intact protein. To test this theory, a compact peptide corresponding to residues 129-142 of staphylococcal nuclease (Ac-EAQAKKEKLNIWS-NH2) was synthesized and its solution structure determined using circular dichroism (CD) and 2D NMR. In aqueous solution, the peptide exhibits CD spectra characteristic of a nascent helix. This nascent helical structure is stabilized by the addition of 2,2,2-trifluoroethanol. Under these conditions, the chemical shift indexes of the 1H alpha and 13C alpha resonances, temperature coefficients of amide protons, and NOE constraints are all consistent with the peptide's structure being a helix-turn. This structure is almost identical to that found in the intact protein.
蛋白质中的紧密区域被认为对应于结构域。如果这是真的，从蛋白质中切除的紧密区域的结构应该与完整蛋白质中的结构非常相似。为了验证这一理论，合成了一种对应于葡萄球菌核酸酶129 - 142位残基的紧密肽（Ac-EAQAKKEKLNIWS-NH2），并使用圆二色性（CD）和二维核磁共振（2D NMR）确定其溶液结构。在水溶液中，该肽呈现出新生螺旋的CD光谱特征。通过添加2,2,2 - 三氟乙醇可稳定这种新生螺旋结构。在这些条件下，1Hα和13Cα共振的化学位移指数、酰胺质子的温度系数以及核Overhauser效应（NOE）约束都与该肽的结构为螺旋 - 转角一致。这种结构几乎与在完整蛋白质中发现的结构相同。
