Pitossi F, Blank A, Schröder A, Schwarz A, Hüssi P, Schwemmle M, Pavlovic J, Staeheli P
Department of Virology, University of Freiburg, Germany.
J Virol. 1993 Nov;67(11):6726-32. doi: 10.1128/JVI.67.11.6726-6732.1993.
Mx proteins are interferon-induced GTPases that inhibit the multiplication of certain negative-stranded RNA viruses. However, it has been unclear whether GTPase activity is necessary for antiviral function. Here, we have introduced mutations into the tripartite GTP-binding consensus elements of the human MxA and mouse Mx1 proteins. The invariant lysine residue of the first consensus motif, which interacts with the beta- and gamma-phosphates of bound GTP in other GTPases, was deleted or replaced by methionine or alanine. These Mx mutants and appropriate controls were then tested for antiviral activity, GTP-binding capacity, and GTPase activity. We found a direct correlation between the GTP-binding capacities and GTP hydrolysis activities of the purified Mx mutants in vitro and their antiviral activities in transfected 3T3 cells, demonstrating that a functional GTP-binding motif is necessary for virus inhibition. Our results, thus, firmly establish antiviral activity as a novel function of a GTPase, emphasizing the enormous functional diversity of GTPase superfamily members.
Mx蛋白是干扰素诱导的GTP酶，可抑制某些负链RNA病毒的增殖。然而，GTP酶活性对于抗病毒功能是否必要尚不清楚。在此，我们对人MxA和小鼠Mx1蛋白的三联GTP结合共有元件引入了突变。第一个共有基序的不变赖氨酸残基，它在其他GTP酶中与结合的GTP的β和γ磷酸相互作用，被缺失或被甲硫氨酸或丙氨酸取代。然后测试这些Mx突变体和适当的对照的抗病毒活性、GTP结合能力和GTP酶活性。我们发现在体外纯化的Mx突变体的GTP结合能力和GTP水解活性与其在转染的3T3细胞中的抗病毒活性之间存在直接相关性，表明功能性GTP结合基序对于病毒抑制是必要的。因此，我们的结果牢固地确立了抗病毒活性作为GTP酶的一种新功能，强调了GTP酶超家族成员的巨大功能多样性。
