Morton C J, Bai H, Zhang J G, Hammacher A, Norton R S, Simpson R J, Mabbutt B C
Joint Protein Structure Laboratory, Ludwig Institute for Cancer Research, Parkville, Vic., Australia.
Biochim Biophys Acta. 1995 Jun 12;1249(2):189-203. doi: 10.1016/0167-4838(95)00023-n.
The effects of solvent, pH and temperature on the 1H-NMR spectra of recombinant murine interleukin-6 (IL-6) are described. Assignments made from two-dimensional homonuclear spectra are presented for resonances of the fifteen aromatic amino-acid side chains. A time-dependent loss of intensity was observed for all resonances in the spectrum of IL-6, probably as a result of aggregation. This aggregation is markedly temperature-dependent. The pKa values of the four histidine residues in murine IL-6 has been measured; one has a value of 5.5, approx. one pH unit less than the value exhibited by the other three. Analysis of the NOESY spectra has allowed a preliminary characterisation of the nature of interactions among the aromatic side chains within the protein fold. 1H and 15N resonances of residues Thr-4 to Val-21 are assigned from three-dimensional 1H-15N correlated spectroscopy, and evidence is presented for these residues comprising a mobile N-terminal tail with little ordered structure. An N-terminal mutant lacking the first 22 residues of the murine IL-6 sequence and known to possess full biological activity was also examined and shown to have essentially retained the tertiary fold of the native molecule.
描述了溶剂、pH值和温度对重组小鼠白细胞介素-6（IL-6）的1H-NMR谱的影响。给出了从二维同核谱对15个芳香族氨基酸侧链共振的归属。观察到IL-6谱中所有共振的强度随时间而损失，这可能是聚集的结果。这种聚集明显依赖于温度。测定了小鼠IL-6中四个组氨酸残基的pKa值；其中一个的值为5.5，比其他三个的值大约低一个pH单位。对NOESY谱的分析使得能够初步表征蛋白质折叠内芳香族侧链之间相互作用的性质。从三维1H-15N相关光谱确定了Thr-4至Val-21残基的1H和15N共振，并提供了这些残基构成几乎没有有序结构的可移动N端尾部的证据。还检测了一个缺少小鼠IL-6序列前22个残基且已知具有完全生物活性的N端突变体，结果表明其基本上保留了天然分子的三级折叠。
