Department of Plant-Microbe Interactions, Max-Planck Institut für Pflanzenzüchtungsforschung, Carl-von-Linne Weg 10, 50829 Cologne, Germany.
Beijing Normal University, Haidian District, 19 Xinjiekouwai Street, 100875 Beijing, China; National Institute of Biological Sciences, Number 7 Science Park Road, Zhongguancun Life Science Park, 102206 Beijing, China.
Cell Host Microbe. 2011 Mar 17;9(3):187-199. doi: 10.1016/j.chom.2011.02.008.
Plants and animals have evolved structurally related innate immune sensors, designated NLRs, to detect intracellular nonself molecules. NLRs are modular, consisting of N-terminal coiled-coil (CC) or TOLL/interleukin-1 receptor (TIR) domains, a central nucleotide-binding (NB) domain, and C-terminal leucine-rich repeats (LRRs). The polymorphic barley mildew A (MLA) locus encodes CC-containing allelic immune receptors recognizing effectors of the pathogenic powdery mildew fungus. We report the crystal structure of an MLA receptor's invariant CC domain, which reveals a rod-shaped homodimer. MLA receptors also self-associate in vivo, but self-association appears to be independent of effector-triggered receptor activation. MLA CC mutants that fail to self-interact impair in planta cell death activity triggered by the CC domain alone and by an autoactive full-length MLA receptor that mimics its ATP-bound state. Thus, CC domain-dependent dimerization of the immune sensor defines a minimal functional unit and implies a role for the dimeric CC module in downstream immune signaling.
动植物已经进化出结构相关的先天免疫传感器，称为 NLRs，以检测细胞内的非自身分子。NLRs 是模块化的，由 N 端卷曲螺旋（CC）或 Toll/白细胞介素-1 受体（TIR）结构域、中央核苷酸结合（NB）结构域和 C 端亮氨酸丰富重复（LRR）组成。多态性大麦白粉病 A（MLA）基因座编码含有 CC 的等位基因免疫受体，识别致病性白粉菌的效应物。我们报告了一个 MLA 受体不变 CC 结构域的晶体结构，该结构揭示了一个棒状同源二聚体。MLA 受体也在体内自我缔合，但自我缔合似乎不依赖于效应物触发的受体激活。无法自我相互作用的 MLA CC 突变体，会削弱由 CC 结构域单独和模拟其 ATP 结合状态的自身激活全长 MLA 受体触发的植物体内细胞死亡活性。因此，免疫传感器的 CC 结构域依赖性二聚化定义了一个最小的功能单位，并暗示二聚体 CC 模块在下游免疫信号中的作用。
