State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China.
PLoS One. 2010 Oct 7;5(10):e13202. doi: 10.1371/journal.pone.0013202.
The ubiquitin-interacting motif (UIM) is a short peptide with dual function of binding ubiquitin (Ub) and promoting ubiquitination. We elucidated the structures and dynamics of the tandem UIMs of ataxin-3 (AT3-UIM12) both in free and Ub-bound forms. The solution structure of free AT3-UIM12 consists of two α-helices and a flexible linker, whereas that of the Ub-bound form is much more compact with hydrophobic contacts between the two helices. NMR dynamics indicates that the flexible linker becomes rigid when AT3-UIM12 binds with Ub. Isothermal titration calorimetry and NMR titration demonstrate that AT3-UIM12 binds diUb with two distinct affinities, and the linker plays a critical role in association of the two helices in diUb binding. These results provide an implication that the tandem UIM12 interacts with Ub or diUb in a cooperative manner through an allosteric effect and dynamics change of the linker region, which might be related to its recognitions with various Ub chains and ubiquitinated substrates.
泛素相互作用基序（UIM）是一种具有双重功能的短肽，既能结合泛素（Ub），又能促进泛素化。我们阐明了三联 UIM 的结构和动力学ataxin-3（AT3-UIM12）在游离和 Ub 结合形式下。游离 AT3-UIM12 的溶液结构由两个α-螺旋和一个柔性接头组成，而 Ub 结合形式则更为紧凑，两个螺旋之间存在疏水接触。NMR 动力学表明，当 AT3-UIM12 与 Ub 结合时，柔性接头变得刚性。等温滴定量热法和 NMR 滴定表明，AT3-UIM12 以两种不同的亲和力结合双 Ub，接头在双 Ub 结合中两个螺旋的结合中起关键作用。这些结果表明，串联 UIM12 通过变构效应和接头区域的动力学变化，以协同方式与 Ub 或双 Ub 相互作用，这可能与其与各种 Ub 链和泛素化底物的识别有关。
