Involvement of the C-terminal disulfide-bonded loop of murine leukemia virus SU protein in a postbinding step critical for viral entry
Involvement of the C-terminal disulfide-bonded loop of murine leukemia virus SU protein in a postbinding step critical for viral entry
复制标题
DOI：
10.1128/jvi.79.12.7868-7876.2005
复制
发表时间：
2005-06-01
影响因子：
5.4
通讯作者：
Pinter, A
中科院分区：
文献类型：
--
作者：
Burkhart, MD;D'Agostino, P;Pinter, A
小鼠白血病病毒（MuLV）Env蛋白C-末端结构域（CTD）在病毒融合中的作用由两种大鼠单克隆抗体（MAbs）对CTD中表位的特异性对MuLV诱导的融合而非受体结合的有效抑制来指示。虽然这两个单克隆抗体，35156和83 A25，有非常不同的模式与病毒分离株的反应性，两个表位的决定簇被映射到最后的C-末端二硫键键环的SU（环10），并在这个环中的残基负责这些单克隆抗体的不同特异性进行了鉴定。这两种单克隆抗体与一小部分截短的SU片段反应，终止环10后的4个残基，表明虽然删除的C-末端残基不是这些表位的一部分，但它们促进了它们的形成。这两种单克隆抗体都不识别以分离形式表达的环10区，表明这些表位不完全位于环10内，而是需要位于环N端的额外序列。环10在融合中的作用的直接支持是由以下证明提供的：在环的第二和第三位置之间含有额外的丝氨酸或苏氨酸残基的Env突变体的感染性高度减弱，并且在融合测定中有缺陷，尽管表达、加工和受体结合的野生型水平。环10的位置1至3处的其他突变抑制gPr 80前体蛋白的加工或导致SU的脱落增加，表明环10也影响Env折叠以及SU和TM之间相互作用的稳定性。
A role for the C-terminal domain (CTD) of murine leukemia virus (MuLV) Env protein in viral fusion was indicated by the potent inhibition of MuLV-induced fusion, but not receptor binding, by two rat monoclonal antibodies (MAbs) specific for epitopes in the CTD. Although these two MAbs, 35156 and 83A25, have very different patterns of reactivity with viral isolates, determinants of both epitopes were mapped to the last C-terminal disulfide-bonded loop of SU (loop 10), and residues in this loop responsible for the different specificities of these MAbs were identified. Both MAbs reacted with a minor fraction of a truncated SU fragment terminating four residues after loop 10, indicating that while the deleted C-terminal residues were not part of these epitopes, they promoted their formation. Neither MAb recognized the loop 10 region expressed in isolated form, suggesting that these epitopes were not completely localized within loop 10 but required additional sequences located N terminal to the loop. Direct support for a role for loop 10 in fusion was provided by the demonstration that Env mutants containing an extra serine or threonine residue between the second and third positions of the loop were highly attenuated for infectivity and defective in fusion assays, despite wild-type levels of expression, processing, and receptor binding. Other mutations at positions I to 3 of loop 10 inhibited processing of the gPr80 precursor protein or led to increased shedding of SU, suggesting that loop 10 also affects Env folding and the stability of the interaction between SU and TM.