Mueller Thomas D, Feigon Juli
Department of Chemistry and Biochemistry, 405 Hilgard Avenue, PO Box 951569, University of California, Los Angeles, CA 90095-1569, USA.
EMBO J. 2003 Sep 15;22(18):4634-45. doi: 10.1093/emboj/cdg467.
HHR23A, a protein implicated in nucleotide excision repair, belongs to a class of proteins containing both a ubiquitin-like (Ubl) domain and one or more ubiquitin-associated (UBA) domains, suggesting a role in the ubiquitin-proteasome pathway as well. The Ubl domain binds with high affinity to the second ubiquitin-interacting motif (UIM) of the S5a subunit of the proteasome. Here we present the solution structures of the HHR23A Ubl domain, the second UIM of S5a (UIM-2), and the Ubl:S5a-UIM-2 complex. The HHR23A Ubl domain is structurally similar to ubiquitin. The S5a UIM forms an alpha-helix with an unexpected hairpin loop that contributes to the binding interface with Ubl. The molecular determinants of the Ubl-proteasome interaction are revealed by analysis of the structures, chemical shift mapping, mutant binding studies and sequence conservation.
HHR23A是一种与核苷酸切除修复相关的蛋白质，属于一类既包含类泛素（Ubl）结构域又包含一个或多个泛素相关（UBA）结构域的蛋白质，这表明它在泛素-蛋白酶体途径中也发挥作用。Ubl结构域与蛋白酶体S5a亚基的第二个泛素相互作用基序（UIM）具有高亲和力结合。本文我们展示了HHR23A Ubl结构域、S5a的第二个UIM（UIM-2）以及Ubl:S5a-UIM-2复合物的溶液结构。HHR23A Ubl结构域在结构上与泛素相似。S5a UIM形成一个带有意外发夹环的α螺旋，该发夹环有助于与Ubl的结合界面。通过对结构的分析、化学位移图谱、突变体结合研究和序列保守性揭示了Ubl-蛋白酶体相互作用的分子决定因素。
