The human IκB Kinase (IKK) is a multisubunit protein complex of two kinases and one scaffolding subunit that controls induction of transcription factor NF-κB activity. IKK behaves as an entity of aberrantly high apparent molecular weight in solution. Recent X-ray crystallographic and cryo-electron microscopy structures of individual catalytic subunits (IKK1/IKKα and IKK2/IKKβ) reveal that they are both stably folded dimeric proteins that engage in extensive homo-oligomerization through unique surfaces that are required for activation of their respective catalytic activities. The NEMO/IKKγ subunit is a predominantly coiled coil protein that is required for activation of IKK through the canonical NF-κB signaling pathway. Here we report size-exclusion chromatography, multi-angle light scattering, analytical centrifugation, and thermal denaturation analyses of full-length human recombinant NEMO as well as deletion and disease-linked variants. We observe that NEMO is predominantly a dimer in solution, although by virtue of its modular coiled coil regions NEMO exhibits complicated solution dynamics involving portions that are mutually antagonistic toward homodimerization. This behavior causes NEMO to behave as a significantly larger sized particle in solution. Analyses of NEMO in complex with IKK2 indicate that NEMO preserves this structurally dynamic character within the multisubuit complex and provides the complex-bound IKK2 further propensity toward homo-oligomerization. These observations provide critical information on the structural plasticity of NEMO subunit dimers which helps clarify its role in diseases and in IKK regulation through oligomerization-dependent phosphorylation of catalytic IKK2 subunit dimers.

人IκB激酶（IKK）是一种多亚基蛋白复合物，由两种激酶和一个支架亚基组成，可控制转录因子NF-κB活性的诱导。IKK表现为溶液中表观分子量异常高的实体。单个催化亚基（IKK1 /IKKα和IKK2 /IKKβ）的最新X射线晶体学和低温电子显微镜结构表明，它们都是稳定折叠的二聚体蛋白，它们通过激活其所需的独特表面参与广泛的均聚。各自的催化活性。NEMO /IKKγ亚基主要是卷曲的卷曲蛋白，它是通过规范的NF-κB信号通路激活IKK所必需的。在这里，我们报告了体积排阻色谱，多角度光散射，分析离心，全长人重组NEMO以及缺失和疾病相关变体的热变性分析。我们观察到NEMO主要是溶液中的二聚体，尽管NEMO由于其模块化的盘绕线圈区域而显示出复杂的溶液动力学，其中包括对同二聚体相互拮抗的部分。此行为导致NEMO在溶液中表现为明显更大的粒子。NEMO与IKK2的复合物的分析表明，NEMO在多子复合物中保留了这种结构动力学特征，并提供了与复合物结合的IKK2进一步倾向于均聚的倾向。