In Gram-positive bacteria, a thick cross-linked cell wall separates the membrane from the extracellular space. Some surface-exposed proteins, such as the Listeria monocytogenes actin nucleation-promoting factor ActA, remain associated with the bacterial membrane but somehow thread through tens of nanometres of cell wall to expose their amino terminus to the exterior. Here, we report that entropy enables the translocation of disordered transmembrane proteins through the Gram-positive cell wall. We build a physical model, which predicts that the entropic constraint imposed by a thin periplasm is sufficient to drive the translocation of an intrinsically disordered protein such as ActA across a porous barrier similar to a peptidoglycan cell wall. We experimentally validate our model and show that ActA translocation depends on the cell-envelope dimensions and disordered-protein length, and that translocation is reversible. We also show that disordered regions of eukaryotic proteins can translocate Gram-positive cell walls via entropy. We propose that entropic forces are sufficient to drive the translocation of specific proteins to the outer surface.

在革兰氏阳性细菌中，厚的交联细胞壁将细胞膜与细胞外空间隔开。一些表面暴露的蛋白质，例如单核细胞增生李斯特菌肌动蛋白成核促进因子 ActA，仍然与细菌膜结合，但不知何故穿过数十纳米的细胞壁，将其氨基末端暴露在外。在这里，我们报告熵使无序跨膜蛋白能够通过革兰氏阳性细胞壁易位。我们建立了一个物理模型，该模型预测由薄周质施加的熵约束足以驱动本质上无序的蛋白质（例如 ActA）穿过类似于肽聚糖细胞壁的多孔屏障的易位。我们通过实验验证了我们的模型，并表明 ActA 易位取决于细胞包膜尺寸和无序蛋白质长度，并且易位是可逆的。我们还表明，真核蛋白质的无序区域可以通过熵转移革兰氏阳性细胞壁。我们提出熵力足以驱动特定蛋白质向外表面的易位。