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Structure and Analysis of R1 and R2 Pyocin Receptor-Binding Fibers

Sergey A Buth1, Mikhail M Shneider2,3, Dean Scholl4

  • 1Institute of Physics of Biologic Systems, École Polytechnique Fédérale de Lausanne (EPFL), BSP-415, 1015 Lausanne, Switzerland. sebuth@utmb.edu.

Viruses
|August 17, 2018
PubMed

Insights

R-type pyocins are antibacterial proteins from Pseudomonas aeruginosa that kill other strains. Their tail fibers, crucial for target recognition and sheath contraction, have now had their crystal structures elucidated.

Area of Science:

  • Microbiology
  • Structural Biology
  • Biochemistry

Background:

  • R-type pyocins are high-molecular weight bacteriocins produced by Pseudomonas aeruginosa.
  • They are structurally analogous to contractile bacteriophage tails.
  • Pyocins utilize tail fibers for target cell recognition and binding.

Purpose of the Study:

  • To determine the crystal structures of the C-terminal fragments of R1 and R2 pyocin fibers.
  • To elucidate the structural basis of receptor binding and sheath contraction triggering.

Main Methods:

  • X-ray crystallography was used to determine the structures of C-terminal fragments of R1 and R2 pyocin fibers.
  • Structural analysis focused on the receptor-binding domains and overall homotrimeric assembly.

Main Results:

  • The crystal structures reveal that both R1 and R2 pyocin fibers are homotrimers, approximately 240 Å long.
  • Each fiber comprises alternating rod-like and globular domains, including N-terminal knob domains and a C-terminal lectin-like domain.
  • Putative substrate binding sites are ~100 Å apart, suggesting a conformational change upon cell surface binding.

Conclusions:

  • The determined structures provide detailed insights into the architecture of pyocin tail fibers.
  • The findings suggest a mechanism where cell surface binding induces a conformational change, initiating sheath contraction for bacterial cell lysis.
Keywords:
Pseudomonas aeruginosaR-type pyocinX-ray crystallographybacteriocincontractile injection systemsreceptor-binding protein

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