BAFF/BLyS receptor 3 comprises a minimal TNF receptor-like module that encodes a highly focused ligand-binding site
BAFF/BLyS receptor 3 comprises a minimal TNF receptor-like module that encodes a highly focused ligand-binding site
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DOI：
10.1021/bi034017g
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发表时间：
2003-05-27
期刊：
影响因子：
2.9
通讯作者：
Starovasnik, MA
中科院分区：
文献类型：
--
作者：
Gordon, NC;Pan, B;Starovasnik, MA
Baff/BLyS是肿瘤坏死家族超家族中的一员，是B细胞的重要生存因子。BAFF结合TACI、BCMA和BR3三种受体，通过BR3传递信号对促进B细胞功能至关重要。典型的肿瘤坏死因子受体(TNFR)家族成员通过与两个富含半胱氨酸的结构域(CRD)相互作用而与其同源配体结合。然而，BR3的胞外区(ECD)只由部分CRD组成，半胱氨酸间距与前面描述的其他模块不同。在这里，我们报告了BR3ECD的溶液结构。核心区只有19个残基，在溶液中具有稳定的结构。BR3折叠类似于上半场C！属于正则TNFR CRD，但由额外的非正则二硫键稳定。用鸟枪法对噬菌体表达的BR3ECD进行丙氨酸扫描诱变，鉴定BAFF结合决定簇。几个关键的BAFF结合残基是从Beta转折中提出的，我们以前已经证明当转移到结构化的Beta-发夹支架时，足以与配体结合[Kayagaki，N.，yan，M.，Seshasayee，D.，Wang，H.，Lee，W.，French，D.，Grewal，I.S.，Cochran，A.G.，Gordon，N.C.，Yen，J.，Starovasnik，M.A.和Dixit，V.M.(2002)免疫力10,515-524]。在该回合之外，突变识别出额外的疏水接触，增强了BAFF-BR3的相互作用。最小发夹肽bhpBR3与BAFF络合物的晶体结构表明，六个残基BR3紧密堆积在配体表面形成空洞。因此，BR3通过一个高度集中的相互作用位点结合BAFF，这在TNFR家族中是前所未有的。
BAFF/BLyS, a member of the tumor necrosis family (TNF) superfamily of ligands, is a crucial survival factor for B cells. BAFF binds three receptors, TACI, BCMA, and BR3, with signaling through BR3 being essential for promoting B cell function. Typical TNF receptor (TNFR) family members bind their cognate ligands through interactions with two cysteine-rich domains (CRDs). However, the extracellular domain (ECD) of BR3 consists of only a partial CRD, with cysteine spacing distinct from other modules described previously. Herein, we report the solution structure of the BR3 ECD. A core region of only 19 residues adopts a stable structure in solution. The BR3 fold is analogous to the first half C! of a canonical TNFR CRD but is stabilized by an additional noncanonical disulfide bond. BAFF-binding determinants were identified by shotgun alanine-scanning mutagenesis of the BR3 ECD expressed on phage. Several of the key BAFF-binding residues are presented from a beta-turn that we have shown previously to be sufficient for ligand binding when transferred to a structured beta-hairpin scaffold [Kayagaki, N., Yan, M., Seshasayee, D., Wang, H., Lee, W., French, D. M., Grewal, I. S., Cochran, A. G., Gordon, N. C., Yin, J., Starovasnik, M. A, and Dixit, V. M. (2002) Immunity 10, 515-524]. Outside of the turn, mutagenesis identifies additional hydrophobic contacts that enhance the BAFF-BR3 interaction. The crystal structure of the minimal hairpin peptide, bhpBR3, in complex with BAFF reveals intimate packing of the six-residue BR3 turn into a cavity on the ligand surface. Thus, BR3 binds BAFF through a highly focused interaction site, unprecedented in the TNFR family.