AimB Is a Small Protein Regulator of Cell Size and MreB Assembly
AimB Is a Small Protein Regulator of Cell Size and MreB Assembly
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DOI：
10.1016/j.bpj.2020.04.029
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发表时间：
2020-08-04
影响因子：
3.4
通讯作者：
Klein，Eric A.
中科院分区：
文献类型：
--
作者：
Werner，John N.;Shi，Handuo;Klein，Eric A.
MreB肌动蛋白样细胞骨架组装成动态聚合物，协调许多细菌中的细胞形状。与大多数其他细胞骨架系统相反，很少有MreB相互作用蛋白被很好地表征。在这里，我们确定了一个小蛋白从新月柄杆菌，MreB（AimB）的装配抑制剂。AimB过表达模拟MreB聚合的抑制，导致细胞宽度增加和MreB离域。此外，aimB似乎是必不可少的，它的耗尽导致细胞宽度减少和对A22（MreB组装的小分子抑制剂）的抗性增加。分子动力学模拟表明，AimB在其单体-单体原丝相互作用裂隙处与MreB结合，并且这种相互作用对新月体MreB优于大肠杆菌MreB，因为AimB的开放程度与AimB的大小更接近，这表明AimB与MreB在新月体中的构象动力学协同进化。我们通过对AimB和MreB中的点突变体的功能分析、与位点特异性非天然氨基酸的光交联研究以及AimB的物种特异性活性来支持该模型。总之，我们的研究结果与AimB通过抑制单体-单体组装相互作用促进MreB动力学一致，代表了调节肌动蛋白样聚合物的新机制和首次鉴定出非毒素MreB组装抑制剂。由于AimB只有104个氨基酸，并且小蛋白质的特征往往很差，因此我们的工作表明在该类中发现更多细菌细胞骨架调节剂的可能性。因此，像FtsZ和真核细胞肌动蛋白，MreB可能有丰富的调控库，以调整其精确的组装和动力学。
The MreB actin-like cytoskeleton assembles into dynamic polymers that coordinate cell shape in many bacteria. In contrast to most other cytoskeleton systems, few MreB-interacting proteins have been well characterized. Here, we identify a small protein fromCaulobacter crescentus, an assembly inhibitor of MreB (AimB). AimB overexpression mimics inhibition of MreB polymerization, leading to increased cell width and MreB delocalization. Furthermore,aimBappears to be essential, and its depletion results in decreased cell width and increased resistance to A22, a small-molecule inhibitor of MreB assembly. Molecular dynamics simulations suggest that AimB binds MreB at its monomer-monomer protofilament interaction cleft and that this interaction is favored forC. crescentusMreB overEscherichia coliMreB because of a closer match in the degree of opening with AimB size, suggesting coevolution of AimB with MreB conformational dynamics inC. crescentus. We support this model through functional analysis of point mutants in both AimB and MreB, photo-cross-linking studies with site-specific unnatural amino acids, and species-specific activity of AimB. Together, our findings are consistent with AimB promoting MreB dynamics by inhibiting monomer-monomer assembly interactions, representing a new mechanism for regulating actin-like polymers and the first identification of a non-toxin MreB assembly inhibitor. Because AimB has only 104 amino acids and small proteins are often poorly characterized, our work suggests the possibility of more bacterial cytoskeletal regulators to be found in this class. Thus, like FtsZ and eukaryotic actin, MreB may have a rich repertoire of regulators to tune its precise assembly and dynamics.