Donaldson Logan W, Wojtyra Urszula, Houry Walid A
Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada.
J Biol Chem. 2003 Dec 5;278(49):48991-6. doi: 10.1074/jbc.M307826200. Epub 2003 Oct 1.
ClpX (423 amino acids), a member of the Clp/Hsp100 family of molecular chaperones and the protease, ClpP, comprise a multimeric complex supporting targeted protein degradation in Escherichia coli. The ClpX sequence consists of an NH2-terminal zinc binding domain (ZBD) and a COOH-terminal ATPase domain. Earlier, we have demonstrated that the zinc binding domain forms a constitutive dimer that is essential for the degradation of some ClpX substrates such as gammaO and MuA but is not required for the degradation of other substrates such as green fluorescent protein-SsrA. In this report, we present the NMR solution structure of the zinc binding domain dimer. The monomer fold reveals that ZBD is a member of the treble clef zinc finger family, a motif known to facilitate protein-ligand, protein-DNA, and protein-protein interactions. However, the dimeric ZBD structure is not related to any protein structure in the Protein Data Bank. A trimer-of-dimers model of ZBD is presented, which might reflect the closed state of the ClpX hexamer.
ClpX（423个氨基酸）是分子伴侣Clp/Hsp100家族的成员，与蛋白酶ClpP组成一个多聚体复合物，支持大肠杆菌中的靶向蛋白质降解。ClpX序列由一个NH2端锌结合结构域（ZBD）和一个COOH端ATP酶结构域组成。此前，我们已经证明锌结合结构域形成一个组成型二聚体，这对于某些ClpX底物（如γO和MuA）的降解至关重要，但对于其他底物（如绿色荧光蛋白-SsrA）的降解则不是必需的。在本报告中，我们展示了锌结合结构域二聚体的核磁共振溶液结构。单体折叠显示ZBD是三叶草形锌指家族的成员，该基序已知有助于蛋白质-配体、蛋白质-DNA和蛋白质-蛋白质相互作用。然而，二聚体ZBD结构与蛋白质数据库中的任何蛋白质结构均无关联。本文提出了一个ZBD的二聚体三聚体模型，它可能反映了ClpX六聚体的封闭状态。
