MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 OQH, UK.
Curr Opin Struct Biol. 2010 Jun;20(3):367-76. doi: 10.1016/j.sbi.2010.03.007. Epub 2010 Apr 22.
The role of ubiquitin in many of the known cellular processes, not just protein degradation, is based on its unique ability to bind a range of proteins that are structurally and functionally different. To understand how ubiquitin can bind to proteins with different structures, we review the extent of the conservation and variation that occur in the structures of two free ubiquitins and ubiquitins in 16 complexes that have been determined at high resolution (1.2-2A). Around 80% of the atomic groups in these structures have positions that differ less than 1A. This conserved core provides a rigid platform for flexible loop regions, 39 residues with side chains that can take up different conformations, and a flexible six-residue region at the C-terminus. In most cases the ability of ubiquitin to bind different structures is limited in part by a central set of residues that largely conserve their conformations. The accommodation of differences in binding proteins is enabled by changes in the flexible surface side chains, loop movements, different specific interactions, water molecules in the interface and the flexible C-terminus.
泛素在许多已知的细胞过程中的作用，不仅仅是蛋白质降解，是基于其独特的能力结合一系列结构和功能不同的蛋白质。为了了解泛素如何与具有不同结构的蛋白质结合，我们回顾了在高分辨率（1.2-2A）测定的 16 个复合物中两种游离泛素和泛素的结构中发生的保守和变异的程度。在这些结构中，大约 80%的原子团位置差异小于 1A。这个保守的核心为灵活的环区提供了一个刚性平台，39 个带有侧链的残基可以采用不同的构象，以及一个灵活的六残基 C 末端。在大多数情况下，泛素结合不同结构的能力部分受到一组中央残基的限制，这些残基在很大程度上保持其构象。通过灵活表面侧链的变化、环运动、不同的特定相互作用、界面中的水分子和灵活的 C 末端，使结合蛋白的差异得到适应。
