Characterization and determination of holin protein of Streptococcus suis bacteriophage SMP in heterologous host
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Published on: May 19, 2022
Yibo Shi1, Yaxian Yan, Wenhui Ji
1Department of Animal Science, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai Key Laboratory of Veterinary Biotechnology, 800 Dongchuan Road, Shanghai, People's Republic of China.
Background:
Holins are a group of phage-encoded membrane proteins that control access of phage-encoded endolysins to the peptidoglycan, and thereby trigger the lysis process at a precise time point as the 'lysis clock'. SMP is an isolated and characterized Streptococcus suis lytic phage. The aims of this study were to determine the holin gene, HolSMP, in the genome of SMP, and characterized the function of holin, HolSMP, in phage infection.
Results:
HolSMP was predicted to encode a small membrane protein with three hydrophobic transmembrane helices. During SMP infections, HolSMP was transcribed as a late gene and HolSMP accumulated harmlessly in the cell membrane before host cell lysis. Expression of HolSMP in Escherichia coli induced an increase in cytoplasmic membrane permeability, an inhibition of host cell growth and significant cell lysis in the presence of LySMP, the endolysin of phage SMP. HolSMP was prematurely triggered by the addition of energy poison to the medium. HolSMP complemented the defective λ S allele in a non-suppressing Escherichia coli strain to produce phage plaques.
Conclusions:
Our results suggest that HolSMP is the holin protein of phage SMP and a two-step lysis system exists in SMP.
Insights
The holin protein HolSMP from Streptococcus suis phage SMP was identified and characterized. HolSMP triggers cell lysis by increasing membrane permeability, functioning as a key component of the phage
Area of Science:
- Microbiology
- Molecular Biology
- Virology
Background:
- Holins are phage-encoded proteins regulating lysis.
- Streptococcus suis lytic phage SMP was previously characterized.
- The precise mechanism of SMP-mediated lysis was unknown.
Purpose of the Study:
- Identify the holin gene (HolSMP) in the SMP phage genome.
- Characterize the function of HolSMP during phage infection.
Main Methods:
- Bioinformatic analysis to predict HolSMP structure.
- Gene expression studies in Escherichia coli.
- Functional assays including membrane permeability and complementation tests.
Main Results:
- HolSMP encodes a small membrane protein with three transmembrane helices.
- HolSMP accumulates in the membrane during infection and induces lysis in conjunction with endolysin LySMP.
- HolSMP expression increases membrane permeability and inhibits bacterial growth.
- HolSMP function was confirmed through complementation assays.
Conclusions:
- HolSMP is the functional holin protein of phage SMP.
- Phage SMP utilizes a two-step lysis mechanism involving HolSMP and LySMP.
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