Smolle Michaela, Hay Ronald T, Byron Olwyn
Biomolecular Sciences Building, School of Biology, University of St. Andrews, The North Haugh, St. Andrews KY16 9ST, Scotland, UK.
Biophys Chem. 2004 Mar 1;108(1-3):259-71. doi: 10.1016/j.bpc.2003.10.032.
NFkappaB is an important and ubiquitous transcription factor formed by various homo- and heterodimers of the NFkappaB family. The active transcription factor regulates genes involved in immune, inflammatory and survival responses. Specificity in gene regulation is achieved, at least in part, by the distinct DNA binding preferences of the various homo- and heterodimers and by the complex pathways that lead to signal-induced degradation of the IkappaB inhibitors. Analytical ultracentrifugation and hydrodynamic bead modelling were used to model the solution structures of the NFkappaB family member p50, its inhibitor IkappaBgamma and their complex. Sedimentation equilibrium (SE) and sedimentation velocity (SV) data show that p50 is a dimer in solution with a sedimentation coefficient consistent with a conformation intermediate between the closed conformation observed in the crystal structure of the p50 (N-terminal domain)-p65 heterodimer complexed with IkappaBalpha and the open conformation adopted by p50 when bound to DNA. SE and SV data show that IkappaBgamma is a monomer in solution and is prone to aggregation over time. p50 forms a 2:1 stoichiometric complex with IkappaBgamma in solution with a sedimentation coefficient consistent with a closed conformation for the p50 dimer.
核因子κB（NFκB）是一种重要且普遍存在的转录因子，由NFκB家族的各种同二聚体和异二聚体组成。活性转录因子调控参与免疫、炎症和生存反应的基因。基因调控的特异性至少部分是通过各种同二聚体和异二聚体不同的DNA结合偏好以及导致IkappaB抑制剂信号诱导降解的复杂途径实现的。使用分析超速离心和流体动力学珠子建模对NFκB家族成员p50、其抑制剂IkappaBγ及其复合物的溶液结构进行建模。沉降平衡（SE）和沉降速度（SV）数据表明，p50在溶液中是二聚体，其沉降系数与在与IkappaBα复合的p50（N端结构域）-p65异二聚体晶体结构中观察到的封闭构象和p50与DNA结合时采用的开放构象之间的构象中间体一致。SE和SV数据表明，IkappaBγ在溶液中是单体，并且随着时间的推移容易聚集。p50在溶液中与IkappaBγ形成2:1化学计量比的复合物，其沉降系数与p50二聚体的封闭构象一致。
