Cuthbert Bonnie J, Chen Xiaorui, Burley Kalistyn, Batot Gaëlle, Contreras Heidi, Dixon Shandee, Goulding Celia W
Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, CA 92697, USA.
Department of Pharmaceutical Sciences, University of California Irvine, Irvine, CA 92697, USA.
Microorganisms. 2024 Nov 30;12(12):2465. doi: 10.3390/microorganisms12122465.
(Mtb) is the causative agent of tuberculosis, the world's deadliest infectious disease. Mtb uses a variety of mechanisms to evade the human host's defenses and survive intracellularly. Mtb's oxidative stress response enables Mtb to survive within activated macrophages, an environment with reactive oxygen species and low pH. Dye-decolorizing peroxidase (DyP), an enzyme involved in Mtb's oxidative stress response, is encapsulated in a nanocompartment, encapsulin (Enc), and is important for Mtb's survival in macrophages. Encs are homologs of viral capsids and encapsulate cargo proteins of diverse function, including those involved in iron storage and stress responses. DyP contains a targeting peptide (TP) at its C-terminus that recognizes and binds to the interior of the Enc nanocompartment. Here, we present the crystal structure of the Mtb-Enc•DyP complex and compare it to cryogenic-electron microscopy (cryo-EM) Mtb-Enc structures. Investigation into the canonical pores formed at symmetrical interfaces reveals that the five-fold pore for the Mtb-Enc crystal structure is strikingly different from that observed in cryo-EM structures. We also observe DyP-TP electron density within the Mtb-Enc shell. Finally, investigation into crystallographic small-molecule binding sites gives insight into potential novel avenues by which substrates could enter Mtb-Enc to react with Mtb-DyP.
结核分枝杆菌（Mtb）是全球最致命的传染病——结核病的病原体。Mtb利用多种机制逃避人类宿主的防御并在细胞内存活。Mtb的氧化应激反应使其能够在活化巨噬细胞内生存，活化巨噬细胞内存在活性氧和低pH环境。染料脱色过氧化物酶（DyP）是一种参与Mtb氧化应激反应的酶，被包裹在一个纳米隔室——封装蛋白（Enc）中，对Mtb在巨噬细胞中的存活至关重要。Enc是病毒衣壳的同源物，可包裹具有多种功能的货物蛋白，包括参与铁储存和应激反应的蛋白。DyP在其C末端含有一个靶向肽（TP），该靶向肽可识别并结合到Enc纳米隔室的内部。在此，我们展示了Mtb-Enc•DyP复合物的晶体结构，并将其与低温电子显微镜（cryo-EM）下的Mtb-Enc结构进行比较。对对称界面处形成的典型孔的研究表明，Mtb-Enc晶体结构的五重孔与cryo-EM结构中观察到的孔显著不同。我们还在Mtb-Enc外壳内观察到了DyP-TP的电子密度。最后，对晶体学小分子结合位点的研究为底物进入Mtb-Enc与Mtb-DyP反应的潜在新途径提供了见解。
