Leonchiks A, Liepinsh E, Barishev M, Sharipo A, Masucci M G, Otting G
Microbiology and Tumor Biology Center (MTC), Karolinska Institute, Stockholm, Sweden.
FEBS Lett. 1998 Dec 4;440(3):365-9. doi: 10.1016/s0014-5793(98)01488-4.
Peptide segments of multiple glycine and alanine residues prevent the proteolytic degradation of ubiquitinated proteins by the proteasome. The structure of a Gly/Ala-rich insert in IkappaB alpha was probed by nuclear magnetic resonance (NMR) spectroscopy, comparing IkappaB alpha samples with and without Gly/Ala-rich insert. Narrow 1H-NMR resonances at chemical shifts indicative of random coil conformations were observed in the difference spectrum. circular dichroism (CD) measurements further confirm that the mechanism of protection against proteolytic degradation is not based on structural transition or stabilization caused by the Gly/Ala-rich segment. In addition, most of the N- and C-terminal residues outside the ankyrin repeats in wild-type IkappaB alpha were found to be flexibly disordered.
多个甘氨酸和丙氨酸残基组成的肽段可防止蛋白酶体对泛素化蛋白质的蛋白水解降解。通过核磁共振（NMR）光谱对IκBα中富含甘氨酸/丙氨酸的插入片段的结构进行了探究，比较了有和没有富含甘氨酸/丙氨酸插入片段的IκBα样品。在差谱中观察到化学位移处窄的1H-NMR共振，表明为无规卷曲构象。圆二色性（CD）测量进一步证实，防止蛋白水解降解的机制并非基于富含甘氨酸/丙氨酸片段引起的结构转变或稳定化。此外，发现野生型IκBα中锚蛋白重复序列之外的大多数N端和C端残基是灵活无序的。
