Kato Yusuke S, Fukui Kiyoshi, Suzuki Kazuo
The Institute for Enzyme Research, Tokushima University, 3-18-15 Kuramoto, Tokushima 770-8503, Japan.
Protein Pept Lett. 2016;23(4):372-8. doi: 10.2174/0929866523666160204124406.
Avian influenza H5N1 has shown high mortality rate in human. Non-structural protein 1 (NS1) is a virulence factor of H5N1. Mutation at the 42nd residue within the RNA-binding domain (RBD) of NS1 dramatically changes the degree of pathogenicity of H5N1 in mice. We here studied the impact of this mutation on the function of RBD, and found that RBD with serine at the 42th residue binds double-stranded RNA (dsRNA), whereas that with proline at the 42th residue does not. Analysis of structural models of the RBD proteins with S42 and P42 suggested remarkable difference in the structure of the dsRNA-binding interface, whereas structural analysis by analytical gel filtration and CD measurements did not indicate difference between those RBD proteins. Our results suggest that the single amino acid replacement induces a minor, but global structural change leading to the loss of function of NS1 thereby the change in the degree of pathogenicity.
H5N1型禽流感在人类中显示出高死亡率。非结构蛋白1（NS1）是H5N1的一种毒力因子。NS1的RNA结合结构域（RBD）内第42位残基的突变显著改变了H5N1在小鼠中的致病程度。我们在此研究了这种突变对RBD功能的影响，发现第42位残基为丝氨酸的RBD能结合双链RNA（dsRNA），而第42位残基为脯氨酸的RBD则不能。对具有S42和P42的RBD蛋白结构模型的分析表明，dsRNA结合界面的结构存在显著差异，而通过分析凝胶过滤和圆二色测量进行的结构分析并未表明这些RBD蛋白之间存在差异。我们的结果表明，单个氨基酸替换会引起微小但全局性的结构变化，导致NS1功能丧失，从而使致病程度发生改变。
