Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138.
Department of Molecular Biology, Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114.
Proc Natl Acad Sci U S A. 2023 Jun 13;120(24):e2221064120. doi: 10.1073/pnas.2221064120. Epub 2023 Jun 5.
Semipermeable membranes are a key feature of all living organisms. While specialized membrane transporters in cells can import otherwise impermeable nutrients, the earliest cells would have lacked a mechanism to import nutrients rapidly under nutrient-rich circumstances. Using both experiments and simulations, we find that a process akin to passive endocytosis can be recreated in model primitive cells. Molecules that are too impermeable to be absorbed can be taken up in a matter of seconds in an endocytic vesicle. The internalized cargo can then be slowly released over hours, into the main lumen or putative cytoplasm. This work demonstrates a way by which primitive life could have broken the symmetry of passive permeation prior to the evolution of protein transporters.
半透膜是所有生物的一个关键特征。虽然细胞中的专门膜转运蛋白可以导入原本不可渗透的营养物质，但最早的细胞在营养丰富的情况下缺乏快速导入营养物质的机制。通过实验和模拟，我们发现类似于被动内吞作用的过程可以在模型原始细胞中重现。对于那些渗透性太差而无法被吸收的分子，可以在几秒钟内被内吞小泡吸收。然后，内部化的货物可以在数小时内缓慢释放到主要腔室或假定的细胞质中。这项工作展示了在蛋白质转运体进化之前，原始生命可能打破被动渗透对称性的一种方式。
