Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA.
Dev Cell. 2013 Jun 10;25(5):520-33. doi: 10.1016/j.devcel.2013.04.007. Epub 2013 May 30.
Sorting of ubiquitinated membrane proteins into lumenal vesicles of multivesicular bodies is mediated by the Endosomal Sorting Complex Required for Transport (ESCRT) apparatus and accessory proteins such as Bro1, which recruits the deubiquitinating enzyme Doa4 to remove ubiquitin from cargo. Here we propose that Bro1 works as a receptor for the selective sorting of ubiquitinated cargoes. We found synthetic genetic interactions between BRO1 and ESCRT-0, suggesting that Bro1 functions similarly to ESCRT-0. Multiple structural approaches demonstrated that Bro1 binds ubiquitin via the N-terminal trihelical arm of its middle V domain. Mutants of Bro1 that lack the ability to bind Ub were dramatically impaired in their ability to sort Ub-cargo membrane proteins, but only when combined with hypomorphic alleles of ESCRT-0. These data suggest that Bro1 and other Bro1 family members function in parallel with ESCRT-0 to recognize and sort Ub-cargoes.
泛素化膜蛋白分选到多泡体的腔室中是由内体分选复合物必需运输（ESCRT）装置和辅助蛋白介导的，如 Bro1，它招募去泛素化酶 Doa4 从货物中去除泛素。在这里，我们提出 Bro1 作为泛素化货物选择性分拣的受体发挥作用。我们发现 BRO1 和 ESCRT-0 之间存在合成遗传相互作用，这表明 Bro1 的功能类似于 ESCRT-0。多种结构方法表明，Bro1 通过其中间 V 结构域的 N 端三螺旋臂结合泛素。缺乏结合 Ub 能力的 Bro1 突变体在分拣 Ub-货物膜蛋白的能力上受到严重损害，但仅在与 ESCRT-0 的功能降低等位基因组合时才会受到影响。这些数据表明，Bro1 和其他 Bro1 家族成员与 ESCRT-0 平行发挥作用，以识别和分拣 Ub-货物。
