Mullard Robin M, Sheedlo Michael J
Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota, USA.
mBio. 2025 Jan 8;16(1):e0240524. doi: 10.1128/mbio.02405-24. Epub 2024 Nov 29.
infection is the leading cause of antibiotic-associated, hospital-acquired diarrhea in the USA; the pathology of which is mediated by toxins. The presence of a toxin known as the Transferase (CDT) in some clinical isolates is linked to severe symptoms including increased incidence of reinfection and higher rates of mortality. Despite its apparent importance to pathology, a mechanistic model of how CDT intoxicates cells remains incomplete. Here, we describe a motif composed of acidic and basic residues (the KDKEK motif) that is essential for toxin function. Using Cryogenic Electron Microscopy (Cryo-EM), we highlight an orientation of the KDKEK motif wherein the acidic residues engage structures thought to play an important role during toxin delivery. We thus present a model wherein these interactions prime CDT for entry into host cells. We expect that this model can be extrapolated to other bacterial toxins to understand how they enter cells.IMPORTANCE is the leading cause of hospital-acquired infectious diarrhea in the USA. The pathology that accompanies infection is triggered by toxins produced by the bacterium. One of these, the Transferase (CDT), has been associated with poorer patient outcomes, although a direct connection to CDT activity has remained elusive. Herein, we present new insight into the mechanism of CDT intoxication and define two regions of the toxin as important for its activity. Moreover, we have generated mutants of CDT that retain the ability to assemble but can no longer intoxicate host cells. In the future, we expect these mutants will serve as valuable tools to help elucidate the role of CDT during infection.
在美国，感染是抗生素相关性医院获得性腹泻的主要原因；其病理由毒素介导。一些临床分离株中存在一种名为转移酶（CDT）的毒素，这与严重症状有关，包括再感染发生率增加和死亡率升高。尽管CDT对病理过程显然很重要，但关于它如何使细胞中毒的机制模型仍不完整。在此，我们描述了一个由酸性和碱性残基组成的基序（KDKEK基序），它对毒素功能至关重要。使用低温电子显微镜（Cryo-EM），我们突出了KDKEK基序的一种取向，其中酸性残基与在毒素传递过程中起重要作用的结构相互作用。因此，我们提出了一个模型，其中这些相互作用使CDT为进入宿主细胞做好准备。我们期望这个模型可以推广到其他细菌毒素，以了解它们如何进入细胞。重要性在美国，感染是医院获得性感染性腹泻的主要原因。伴随感染的病理过程是由细菌产生的毒素引发的。其中一种毒素，转移酶（CDT），与较差的患者预后有关，尽管与CDT活性的直接联系一直难以捉摸。在此，我们对CDT中毒机制提出了新的见解，并将毒素的两个区域定义为对其活性很重要。此外，我们已经生成了CDT的突变体，这些突变体保留了组装能力，但不再能使宿主细胞中毒。未来，我们期望这些突变体将成为有价值的工具，以帮助阐明CDT在感染过程中的作用。
