Schreiber M, Rajarathnam K, McFadden G
Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
J Biol Chem. 1996 Jun 7;271(23):13333-41. doi: 10.1074/jbc.271.23.13333.
The myxoma virus T2 (M-T2) gene expresses a secreted protein that contains significant sequence similarity to the ligand binding domains of the cellular tumor necrosis factor (TNF) receptors, specifically inhibits the cytolytic activity of rabbit TNFalpha and is an important virulence factor for myxoma virus infection in rabbits. M-T2 protein was overexpressed from vaccinia virus vectors, purified to apparent homogeneity, and found to specifically protect mouse and rabbit cells from lysis by rabbit TNFalpha at molar ratios comparable with the soluble versions of the host tumor necrosis factor receptors. M-T2 secreted from virus-infected cells is detected as both a monomer and a disulfide-linked dimer, both of which were shown by Scatchard analysis to bind rabbit TNFalpha (Kd values of 170 pM and 195 pM, respectively), values that are comparable with the affinities of mammalian TNFs with their receptors. In contrast to the rabbit ligand, M-T2 interacts with mouse TNFalpha with a much lower affinity, Kd of 1.7 nM, and was unable to inhibit the cytolytic activity of this ligand on mouse cells. Although both monomeric and dimeric forms bound rabbit TNFalpha with comparable affinity, the dimeric M-T2 protein was a far more potent inhibitor of rabbit TNFalpha, presumably because it can more effectively prevent dimerization of TNF receptors than can the M-T2 monomer.
黏液瘤病毒T2（M-T2）基因表达一种分泌蛋白，该蛋白与细胞肿瘤坏死因子（TNF）受体的配体结合域具有显著的序列相似性，能特异性抑制兔TNFα的细胞溶解活性，是黏液瘤病毒感染兔子的重要毒力因子。M-T2蛋白通过痘苗病毒载体过表达，纯化至表观均一，发现在与宿主肿瘤坏死因子受体的可溶性形式相当的摩尔比下，能特异性保护小鼠和兔细胞免受兔TNFα的裂解。病毒感染细胞分泌的M-T2被检测为单体和二硫键连接的二聚体，Scatchard分析表明两者均能结合兔TNFα（Kd值分别为170 pM和195 pM），这些值与哺乳动物TNF与其受体的亲和力相当。与兔配体不同，M-T2与小鼠TNFα的相互作用亲和力低得多，Kd为1.7 nM，且无法抑制该配体对小鼠细胞的细胞溶解活性。尽管单体和二聚体形式与兔TNFα的结合亲和力相当，但二聚体M-T2蛋白是兔TNFα更有效的抑制剂，推测是因为它比M-T2单体能更有效地阻止TNF受体的二聚化。
