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Endolysin Regulation in Phage Mu Lysis.

Jake S Chamblee1, Jolene Ramsey1, Yi Chen1

  • 1Center for Phage Technology, Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA.

Mbio
|April 26, 2022
PubMed
Summary
This summary is machine-generated.

Bacteriophage Mu lacks a holin, a protein essential for lysis in most related viruses. Instead, it uses a novel "releasin" protein to release its endolysin, enabling cell lysis and infection completion.

Keywords:
bacteriophage lysisbacteriophagesmembranes

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Area of Science:

  • Microbiology
  • Virology
  • Molecular Biology

Background:

  • Bacteriophage Mu is a key model organism for studying viral genome replication via transposition.
  • Gram-negative bacterial lysis by Caudovirales phages typically requires a holin, endolysin, and spanin to disrupt the cell envelope.
  • Previous studies identified only one lysis gene (endolysin gp22) in Bacteriophage Mu, posing a puzzle regarding its lysis mechanism.

Purpose of the Study:

  • To elucidate the complete lysis mechanism of Bacteriophage Mu, particularly its apparent lack of a holin.
  • To characterize the identified lysis proteins, including the endolysin gp22 and its role in cell envelope disruption.
  • To identify novel proteins involved in Bacteriophage Mu-mediated host cell lysis.

Main Methods:

  • Nonsense mutant screening to identify lysis genes.
  • Protein characterization, including signal-anchor-release (SAR) endolysin analysis.
  • Mutational analysis to determine protein function and interactions.
  • Bioinformatic analysis of protein families (DUF2730).

Main Results:

  • Bacteriophage Mu utilizes a signal-anchor-release (SAR) endolysin (gp22) and a two-component spanin (gp23 and gp23.1).
  • Mu lacks a holin; instead, it employs a membrane-tethered protein, gp25 (termed "releasin"), for SAR endolysin release.
  • Specific lysine residues in gp22 mediate dependence on gp25 for release.
  • The releasin protein (gp25) facilitates SAR endolysin release from other phages and belongs to the DUF2730 family found in Mu-like phages.

Conclusions:

  • Bacteriophage Mu employs a unique lysis mechanism distinct from other Caudovirales phages by lacking a holin.
  • The newly identified "releasin" protein (gp25) plays a crucial role in SAR endolysin release, representing a novel lysis strategy.
  • These findings offer insights into the evolution of phage lysis systems and the functional diversity of DUF2730 proteins.