Department of Molecular Biology, University of Wyoming, Laramie, WY 82071.
Department of Molecular Biology, University of Wyoming, Laramie, WY 82071
Proc Natl Acad Sci U S A. 2017 Apr 4;114(14):3732-3737. doi: 10.1073/pnas.1700315114. Epub 2017 Mar 20.
The ability to recognize close kin confers survival benefits on single-celled microbes that live in complex and changing environments. Microbial kinship detection relies on perceptible cues that reflect relatedness between individuals, although the mechanisms underlying recognition in natural populations remain poorly understood. In myxobacteria, cells identify related individuals through a polymorphic cell surface receptor, TraA. Recognition of compatible receptors leads to outer membrane exchange among clonemates and fitness consequences. Here, we investigated how a single receptor creates a diversity in recognition across myxobacterial populations. We first show that TraA requires its partner protein TraB to function in cell-cell adhesion. Recognition is shown to be allele-specific, where polymorphisms within TraA dictate binding selectivity. We reveal the malleability of TraA recognition, and seemingly minor changes to its variable region reprogram recognition outcomes. Strikingly, we identify a single residue (A/P205) as a molecular switch for TraA recognition. Substitutions at this position change the specificity of a diverse panel of environmental TraA receptors. In addition, we engineered a receptor with unique specificity by simply creating an A205P substitution, suggesting that modest changes in TraA can lead to diversification of new recognition groups in nature. We hypothesize that the malleable property of TraA has allowed it to evolve and create social barriers between myxobacterial populations and in turn avoid adverse interactions with relatives.
识别近亲的能力赋予了生活在复杂多变环境中的单细胞微生物生存优势。微生物亲缘关系的检测依赖于可感知的线索，这些线索反映了个体之间的亲缘关系，尽管自然种群中识别的机制仍知之甚少。在粘细菌中，细胞通过一种多态的细胞表面受体 TraA 来识别相关个体。对相容受体的识别会导致克隆成员之间的外膜交换和适应度后果。在这里，我们研究了单个受体如何在粘细菌群体中产生多样性的识别。我们首先表明，TraA 需要其伴侣蛋白 TraB 才能在细胞-细胞黏附中发挥作用。识别被证明是等位基因特异性的，TraA 中的多态性决定了结合的选择性。我们揭示了 TraA 识别的可变性，其可变区的微小变化似乎重新编程了识别结果。引人注目的是，我们确定了一个单一的残基（A/P205）作为 TraA 识别的分子开关。该位置的取代会改变多样化的环境 TraA 受体的特异性。此外，我们通过简单地创建 A205P 取代工程化了一个具有独特特异性的受体，这表明 TraA 的适度变化可以导致自然界中新型识别群体的多样化。我们假设 TraA 的可塑特性使其能够进化，并在粘细菌种群之间建立社会障碍，从而避免与亲属的不利相互作用。
