Department of Biology, Stanford University, Stanford, CA 94305, USA.
Dev Cell. 2012 Dec 11;23(6):1247-54. doi: 10.1016/j.devcel.2012.10.023. Epub 2012 Nov 29.
The diversity of ubiquitin (Ub)-dependent signaling is attributed to the ability of this small protein to form different types of covalently linked polyUb chains and to the existence of Ub binding proteins that interpret this molecular syntax. We used affinity capture/mass spectrometry to identify ALIX, a component of the ESCRT pathway, as a Ub binding protein. We report that the V domain of ALIX binds directly and selectively to K63-linked polyUb chains, exhibiting a strong preference for chains composed of more than three Ub. Sequence analysis identified two potential Ub binding sites on a single α-helical surface within the coiled-coil region of the V domain. Mutation of these putative Ub binding sites inhibited polyUb binding to the isolated V domain in vitro and impaired budding of lentiviruses. These data reveal an important role for K63 polyUb binding by ALIX in retroviral release.
泛素（Ub）依赖性信号的多样性归因于这种小蛋白形成不同类型的共价连接多 Ub 链的能力，以及存在 Ub 结合蛋白来解释这种分子语法。我们使用亲和捕获/质谱法鉴定了 ESCRT 途径的一个组成部分 ALIX，作为 Ub 结合蛋白。我们报告说，ALIX 的 V 结构域直接且选择性地结合 K63 连接的多 Ub 链，对由三个以上 Ub 组成的链表现出强烈的偏好。序列分析在 V 结构域的卷曲螺旋区的单个α螺旋表面上鉴定出两个潜在的 Ub 结合位点。在体外，突变这些假定的 Ub 结合位点会抑制多 Ub 与分离的 V 结构域的结合，并损害慢病毒的出芽。这些数据揭示了 ALIX 在逆转录病毒释放中 K63 多 Ub 结合的重要作用。
