Selective recruitment and concentration of signalling proteins within membraneless compartments is a ubiquitous mechanism for subcellular organization^1,2,3. The dynamic flow of molecules into and out of these compartments occurs on faster timescales than for membrane-enclosed organelles, presenting a possible mechanism to control spatial patterning within cells. Here, we combine single-molecule tracking and super-resolution microscopy, light-induced subcellular localization, reaction-diffusion modelling and a spatially resolved promoter activation assay to study signal exchange in and out of the 200 nm cytoplasmic pole-organizing protein popZ (PopZ) microdomain at the cell pole of the asymmetrically dividing bacterium Caulobacter crescentus^4,5,6,7,8. Two phospho-signalling proteins, the transmembrane histidine kinase CckA and the cytoplasmic phosphotransferase ChpT, provide the only phosphate source for the cell fate-determining transcription factor CtrA^{9,10,11,12,13,14,15,16,17,18}. We find that all three proteins exhibit restricted rates of entry into and escape from the microdomain as well as enhanced phospho-signalling within, leading to a submicron gradient of activated CtrA-P¹⁹ that is stable and sublinear. Entry into the microdomain is selective for cytosolic proteins and requires a binding pathway to PopZ. Our work demonstrates how nanoscale protein assemblies can modulate signal propagation with fine spatial resolution, and that in Caulobacter, this modulation serves to reinforce asymmetry and differential cell fate of the two daughter cells.

无膜室内信号蛋白的选择性募集和浓缩是亚细胞组织的普遍机制^1,2,3。分子进出这些区室的动态流动发生的时间尺度比膜封闭的细胞器更快，这提供了一种控制细胞内空间图案的可能机制。在这里，我们结合单分子追踪和超分辨率显微镜、光诱导亚细胞定位、反应扩散模型和空间分辨启动子激活测定来研究 200 nm 细胞质极组织蛋白 popZ (PopZ) 内外的信号交换) 不对称分裂细菌新月柄杆菌^4,5,6,7,8细胞极处的微结构域。两种磷酸信号蛋白，跨膜组氨酸激酶 CckA 和细胞质磷酸转移酶 ChpT，为细胞命运决定转录因子 CtrA 提供唯一的磷酸盐来源^{9,10,11,12,13,14,15,16,17,18}。我们发现所有三种蛋白质都表现出进入和逃离微域的受限速率以及内部磷酸信号传导的增强，从而导致激活的 CtrA-P 19 的亚微米梯度^稳定且亚线性。进入微结构域对胞质蛋白具有选择性，并且需要与 PopZ 的结合途径。我们的工作展示了纳米级蛋白质组装体如何以精细的空间分辨率调节信号传播，并且在柄杆菌中，这种调节有助于增强两个子细胞的不对称性和差异细胞命运。