Self-identity reprogrammed by a single residue switch in a cell surface receptor of a social bacterium.
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 betraAallele-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.
Department of Molecular Biology, University of Wyoming, Laramie, WY 82071.
Pengbo
P
Cao
Department of Molecular Biology, University of Wyoming, Laramie, WY 82071 dwall2@uwyo.edu.
Daniel
D
Wall
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D008958:Models, Molecular; D016941:Myxococcus xanthus / Q000502:physiology*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013045:Species Specificity
D001426:Bacterial Proteins; D011956:Receptors, Cell Surface; C082576:traB protein, Bacteria
Myxococcus xanthus; kin recognition; outer membrane exchange