Subedi Pramod, Paxman Jason J, Wang Geqing, Hor Lilian, Hong Yaoqin, Verderosa Anthony D, Whitten Andrew E, Panjikar Santosh, Santos-Martin Carlos F, Martin Jennifer L, Totsika Makrina, Heras Begoña
Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Australia.
Centre for Immunology and Infection Control, School of Biomedical Sciences, Queensland University of Technology, Brisbane, Australia.
Antioxid Redox Signal. 2021 Jul;35(1):21-39. doi: 10.1089/ars.2020.8218. Epub 2021 Apr 12.
Thioredoxin (TRX)-fold proteins are ubiquitous in nature. This redox scaffold has evolved to enable a variety of functions, including redox regulation, protein folding, and oxidative stress defense. In bacteria, the TRX-like disulfide bond (Dsb) family mediates the oxidative folding of multiple proteins required for fitness and pathogenic potential. Conventionally, Dsb proteins have specific redox functions with monomeric and dimeric Dsbs exclusively catalyzing thiol oxidation and disulfide isomerization, respectively. This contrasts with the eukaryotic disulfide forming machinery where the modular TRX protein disulfide isomerase (PDI) mediates thiol oxidation and disulfide reshuffling. In this study, we identified and structurally and biochemically characterized a novel Dsb-like protein from termed bovine colonization factor protein H (BcfH) and defined its role in virulence. In the conserved bovine colonization factor () fimbrial operon, the Dsb-like enzyme BcfH forms a trimeric structure, exceptionally uncommon among the large and evolutionary conserved TRX superfamily. This protein also displays very unusual catalytic redox centers, including an unwound α-helix holding the redox active site and a proline instead of the conserved -proline active site loop. Remarkably, BcfH displays both thiol oxidase and disulfide isomerase activities contributing to fimbrial biogenesis. Typically, oligomerization of bacterial Dsb proteins modulates their redox function, with monomeric and dimeric Dsbs mediating thiol oxidation and disulfide isomerization, respectively. This study demonstrates a further structural and functional malleability in the TRX-fold protein family. BcfH trimeric architecture and unconventional catalytic sites permit multiple redox functions emulating in bacteria the eukaryotic PDI dual oxidoreductase activity. . 35, 21-39.
硫氧还蛋白（TRX）折叠蛋白在自然界中普遍存在。这种氧化还原支架已经进化到能够实现多种功能，包括氧化还原调节、蛋白质折叠和氧化应激防御。在细菌中，类似TRX的二硫键（Dsb）家族介导了多种对适应性和致病潜力至关重要的蛋白质的氧化折叠。传统上，Dsb蛋白具有特定的氧化还原功能，单体Dsb专门催化硫醇氧化，二聚体Dsb专门催化二硫键异构化。这与真核生物的二硫键形成机制形成对比，在真核生物中，模块化的TRX蛋白二硫键异构酶（PDI）介导硫醇氧化和二硫键重排。在本研究中，我们从牛源中鉴定出一种新型的类似Dsb的蛋白，对其进行了结构和生化特征分析，并确定了其在毒力中的作用。在保守的牛定植因子（BCF）菌毛操纵子中，类似Dsb的酶BcfH形成三聚体结构，这在庞大且进化保守的TRX超家族中极为罕见。这种蛋白还展示了非常不寻常的催化氧化还原中心，包括一个环绕氧化还原活性位点的解旋α螺旋以及一个取代保守的Cys-Pro活性位点环的脯氨酸。值得注意的是，BcfH同时具有硫醇氧化酶和二硫键异构酶活性，有助于BCF菌毛的生物合成。通常，细菌Dsb蛋白的寡聚化会调节其氧化还原功能，单体Dsb和二聚体Dsb分别介导硫醇氧化和二硫键异构化。本研究证明了TRX折叠蛋白家族在结构和功能上具有进一步的可塑性。BcfH的三聚体结构和非常规催化位点允许其具有多种氧化还原功能，在细菌中模拟了真核生物PDI的双氧化还原酶活性。[参考文献]35, 21 - 39。
