AimR Adopts Preexisting Dimer Conformations for Specific Target Recognition in Lysis-Lysogeny Decisions of Bacillus Phage phi3T.

Kai Pei,Tingting Zou,Zhu Liu,Jie Zhang

doi:10.3390/biom11091321

Kai Pei, Tingting Zou + Show 2 more

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https://doi.org/10.3390/biom11091321

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Journal: Biomolecules	Publication Date: Sep 7, 2021
Citations: 8	License type: CC BY 4.0

Affiliation: Huazhong Agricultural University

Abstract

A bacteriophage switches between lytic and lysogenic life cycles. The AimR-AimP-AimX communication system is responsible for phage lysis-lysogeny decisions during the infection of Bacillus subtilis. AimX is a regulator biasing phage lysis, AimR is a transcription factor activating AimX expression, and AimP is an arbitrium peptide that determines phage lysogeny by deactivating AimR. A strain-specific mechanism for the lysis-lysogeny decisions is proposed in SPbeta and phi3T phages. That is, the arbitrium peptide of the SPbeta phage stabilizes the SPbeta AimR (spAimR) dimer, whereas the phi3T-derived peptide disassembles the phi3T AimR (phAimR) dimer into a monomer. Here, we find that phAimR does not undergo dimer-to-monomer conversion upon arbitrium peptide binding. Gel-filtration, static light scattering (SLS) and analytical ultracentrifugation (AUC) results show that phAimR is dimeric regardless of the presence of arbitrium peptide. Small-angle X-ray scattering (SAXS) reveals that the arbitrium peptide binding makes an extended dimeric conformation. Single-molecule fluorescence resonance energy transfer (smFRET) analysis reveals that the phAimR dimer fluctuates among two distinct conformational states, and each preexisting state is selectively recognized by the arbitrium peptide or the target DNA, respectively. Collectively, our biophysical characterization of the phAimR dynamics underlying specific target recognition provides new mechanistic insights into understanding lysis-lysogeny decisions in Bacillus phage phi3T.

Highlights

Consistent with this, by performing gel-filtration assay using Superdex 200 Increase 10/300 GL column, we found that, in the presence of SAIRGA peptide, the peak of phAimRY341A/E371A migrated later than the phAimRY341A/E371A alone peak (Figure 1a,b)
Peptide binding of the wild-type phi3T AimR (phAimR) produced no significant migration differences (Figure 1a,b). These results indicate that the phAimY341A/E371A undergoes a dimer-tomonomer conversion upon peptide binding, whereas the wild-type phAimR adopts a dimer conformation regardless of the presence of peptides
Binding. (a) Gel-filtration analysis assesses the effect of SAIRGA peptide binding on phAimR and phAimRY341A/E371A. (b) visualize the elution volume of the peak fractions in (a)

Summary

Introduction

During the infection of host cells, temperate phages dynamically switch between lytic and lysogenic life cycles to propagate descendants [1,2,3,4]. In the earlier stage of reproduction, the bacteriophage chose a lytic cycle to replicate the phage DNA, assemble the phage particles, release the virions by lysing the host and start a new infection cycle [5,6]. As the nutrients and the number of the hosts in the environment decreased, the bacteriophage switches to the lysogenic cycle. The phage integrates itself into the host genome to propagate along with its host and confers the lysogenized bacteria with immunity against further infection [7,8]. The dynamic transition between the lytic and lysogenic life cycles is vital for phage survival. The lysis-lysogeny decisions of the bacteriophage are regulated by an intracellular communication system between co-infecting phages [9,10,11,12]

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