Biology Department, Brookhaven National Laboratory, Upton, NY 11973-5000, USA.
Structure. 2009 Oct 14;17(10):1377-85. doi: 10.1016/j.str.2009.08.010.
Proteasome-mediated protein turnover in all domains of life is an energy-dependent process that requires ATPase activity. Mycobacterium tuberculosis (Mtb) was recently shown to possess a ubiquitin-like proteasome pathway that plays an essential role in Mtb resistance to killing by products of host macrophages. Here we report our structural and biochemical investigation of Mpa, the presumptive Mtb proteasomal ATPase. We demonstrate that Mpa binds to the Mtb proteasome in the presence of ATPgammaS, providing the physical evidence that Mpa is the proteasomal ATPase. X-ray crystallographic determination of the conserved interdomain showed a five stranded double beta barrel structure containing a Greek key motif. Structure and mutational analysis indicate a major role of the interdomain for Mpa hexamerization. Our mutational and functional studies further suggest that the central channel in the Mpa hexamer is involved in protein substrate translocation and degradation. These studies provide insights into how a bacterial proteasomal ATPase interacts with and facilitates protein degradation by the proteasome.
所有生命领域中的蛋白酶体介导的蛋白质周转是一个依赖能量的过程，需要 ATP 酶活性。最近的研究表明，结核分枝杆菌（Mtb）拥有一种泛素样蛋白酶体途径，该途径在 Mtb 抵抗宿主巨噬细胞产物杀伤方面发挥着重要作用。在这里，我们报告了我们对假定的 Mtb 蛋白酶体 ATP 酶 Mpa 的结构和生化研究。我们证明，在 ATPgammaS 的存在下，Mpa 结合到 Mtb 蛋白酶体上，这提供了 Mpa 是蛋白酶体 ATP 酶的物理证据。保守的结构域间的 X 射线晶体学测定显示了一个包含希腊钥匙模体的五链双β桶结构。结构和突变分析表明，结构域间在 Mpa 六聚体形成中起主要作用。我们的突变和功能研究进一步表明，Mpa 六聚体的中央通道参与蛋白质底物的易位和降解。这些研究为细菌蛋白酶体 ATP 酶如何与蛋白酶体相互作用并促进蛋白质降解提供了深入了解。
