Komander David, Barford David
Section of Structural Biology, The Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB, UK.
Biochem J. 2008 Jan 1;409(1):77-85. doi: 10.1042/BJ20071399.
The NF-kappaB (nuclear factor kappaB) regulator A20 antagonises IKK [IkappaB (inhibitor of kappaB) kinase] activation by modulating Lys63-linked polyubiquitination of cytokine-receptor-associated factors including TRAF2/6 (tumour-necrosis-factor-receptor-associated factor 2/6) and RIP1 (receptor-interacting protein 1). In the present paper we describe the crystal structure of the N-terminal OTU (ovarian tumour) deubiquitinase domain of A20, which differs from other deubiquitinases but shares the minimal catalytic core with otubain-2. Analysis of conserved surface regions allows prediction of ubiquitin-binding sites for the proximal and distal ubiquitin molecules. Structural and biochemical analysis suggests a novel architecture of the catalytic triad, which might be present in a subset of OTU domains including Cezanne and TRABID (TRAF-binding domain). Biochemical analysis shows a preference of the isolated A20 OTU domain for Lys48-linked tetraubiquitin in vitro suggesting that additional specificity factors might be required for the physiological function of A20 in cells.
核因子κB（NF-κB）调节因子A20通过调节包括肿瘤坏死因子受体相关因子2/6（TRAF2/6）和受体相互作用蛋白1（RIP1）在内的细胞因子受体相关因子的赖氨酸63连接的多聚泛素化来拮抗IKK[κB抑制因子（IkappaB）激酶]的激活。在本文中，我们描述了A20的N端卵巢肿瘤（OTU）去泛素酶结构域的晶体结构，它与其他去泛素酶不同，但与otubain-2共享最小催化核心。对保守表面区域的分析允许预测近端和远端泛素分子的泛素结合位点。结构和生化分析表明催化三联体具有一种新的结构，这种结构可能存在于包括Cezanne和TRAF结合结构域（TRABID）在内的OTU结构域子集中。生化分析表明，在体外，分离的A20 OTU结构域对赖氨酸48连接的四聚泛素具有偏好性，这表明细胞中A20的生理功能可能需要额外的特异性因子。
