Topo Elias J, De Santiago Carolina Basurto, Cao Pengbo, Wall Daniel, Nan Beiyan
Department of Biology, Texas A&M University, College Station TX 77843, USA.
Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA.
bioRxiv. 2025 Apr 28:2025.04.25.650704. doi: 10.1101/2025.04.25.650704.
Kin recognition, the ability to distinguish self from nonself at the cellular level is critical to multicellular life. is a multicellular bacterium that cooperates among genetically-related cells and reduces exploitation by nonkin through outer membrane exchange (OME) of common goods and toxins. The polymorphic cell surface receptor called TraA and its partner protein TraB mediate kin recognition by OME, but its molecular mechanism remains unknown. Here we used quantitative microscopy techniques to characterize the stoichiometry of the intracellular TraAB complexes and the intercellular TraA-TraA interactions. We visualized the OME of single protein particles between cells and revealed that OME depends on the free diffusion of outer membrane (OM) contents. Based on the predicted structures, we propose a model that TraAB overcomes the repulsion between OMs by stressing the membranes and reducing the contact area, analogous to the eukaryotic soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), which mediate plasma membrane fusion. Our working model provides a novel pathway that leads to an underlying conserved mechanism for membrane fusion that is a foundation process for multicellularity.
亲缘识别，即在细胞水平上区分自我与非自我的能力，对多细胞生物的生存至关重要。[具体生物名称未译出]是一种多细胞细菌，它在基因相关的细胞间进行合作，并通过共同物质和毒素的外膜交换（OME）减少非亲缘细胞的利用。名为TraA的多态性细胞表面受体及其伴侣蛋白TraB通过OME介导亲缘识别，但其分子机制尚不清楚。在这里，我们使用定量显微镜技术来表征细胞内TraAB复合物的化学计量以及细胞间TraA - TraA相互作用。我们可视化了细胞间单个蛋白质颗粒的OME，并揭示OME依赖于外膜（OM）成分的自由扩散。基于预测的结构，我们提出了一个模型，即TraAB通过对膜施加压力并减小接触面积来克服OM之间的排斥，这类似于真核生物中介导质膜融合的可溶性N - 乙基马来酰亚胺敏感因子附着蛋白受体（SNAREs）。我们的工作模型提供了一条新途径，通向一种潜在的保守膜融合机制，而膜融合是多细胞性的基础过程。
