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A Rapidly Evolving Polybasic Motif Modulates Bacterial Detection by Guanylate Binding Proteins.

Kristin M Kohler1, Miriam Kutsch2, Anthony S Piro2

  • 1Institute of Ecology & Evolution, University of Oregon, Eugene, Oregon, USA.

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|May 21, 2020
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Summary
This summary is machine-generated.

Guanylate binding proteins (GBPs) use a rapidly evolving motif to detect bacteria like Shigella flexneri. This polybasic motif (PBM) evolution drives pathogen recognition specificity in primate immunity.

Keywords:
Shigellacell-autonomous immunityevolutionguanylate binding proteinshost-pathogen interactions

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Area of Science:

  • Immunology
  • Evolutionary Biology
  • Molecular Biology

Background:

  • Cell-autonomous immunity depends on host proteins recognizing intracellular pathogens.
  • Guanylate binding proteins (GBPs) are crucial for vertebrate defense against diverse microbes.
  • Pathogen specificity of human and mouse GBPs is not fully understood.

Purpose of the Study:

  • To investigate the molecular basis of Guanylate binding protein (GBP) pathogen specificity.
  • To determine how rapid evolution of a C-terminal polybasic motif (PBM) influences target recognition.
  • To understand the evolutionary dynamics of GBP function in primate immune defense.

Main Methods:

  • Comparative analysis of primate Guanylate binding protein (GBP) sequences.
  • Functional assays involving swapping of C-terminal polybasic motifs (PBMs) between GBP orthologs.
  • Site-directed mutagenesis to assess the impact of single amino acid substitutions on bacterial detection.

Main Results:

  • Rapid diversification of the C-terminal polybasic motif (PBM) in primate GBPs controls recognition of *Shigella flexneri*.
  • Swapping PBMs between primate GBP1 orthologs demonstrated enhanced or lost targeting ability for *S. flexneri* in specific primate lineages.
  • Single substitutions in rapidly evolving GBP1 PBM sites were sufficient to alter bacterial detection, indicating epistasis.
  • Squirrel monkey GBP2 C-terminal domain recently acquired *S. flexneri* targeting via convergent evolution.

Conclusions:

  • Accelerated evolution of the PBM is a key mechanism shifting GBP target specificity.
  • Epistasis plays a role in the evolution of pathogen recognition by GBPs.
  • Primate GBPs have evolved diverse strategies, including convergent evolution, to adapt their defense against intracellular pathogens like *Shigella flexneri*.