title: PAAR-Rhs proteins harbor various C-terminal toxins to diversify the antibacterial pathways of type VI secretion systems.
abstract: The type VI secretion system (T6SS) of bacteria plays a key role in competing for specific niches by the contact-dependent killing of competitors. Recently, Rhs proteins with polymorphic C-terminal toxin-domains that inhibit or kill neighboring cells were identified. In this report, we identified a novel Rhs with an MPTase4 (Metallopeptidase-4) domain (designated as Rhs-CT1) that showed an antibacterial effect via T6SS in Escherichia coli. We managed to develop a specific strategy by matching the diagnostic domain-architecture of Rhs-CT1 (Rhs with an N-terminal PAAR-motif and a C-terminal toxin domain) for effector retrieval and discovered a series of Rhs-CTs in E. coli. Indeed, the screened Rhs-CT3 with a REase-3 (Restriction endonuclease-3) domain also mediated interbacterial antagonism. Further analysis revealed that vgrGO1and eagR/DUF1795 (upstream of rhs-ct) were required for the delivery of Rhs-CTs, suggesting eagR as a potential T6SS chaperone. In addition to chaperoned Rhs-CTs, neighborless Rhs-CTs could be classified into a distinct family (Rhs-Nb) sharing close evolutionary relationship with T6SS2-Rhs (encoded in the T6SS2 cluster of E. coli). Notably, the Rhs-Nb-CT5 was confirmed bioinformatically and experimentally to mediate interbacterial antagonism via Hcp2B-VgrG2 module. In a further retrieval analysis, we discovered various toxin/immunity pairs in extensive bacterial species that could be systematically classified into eight referential clans, suggesting that Rhs-CTs greatly diversify the antibacterial pathways of T6SS.
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China.|Ministry of Agriculture, Key Lab of Animal Bacteriology, Nanjing, 210095, China.
authors.forename: Jiale
authors.initials: J
authors.lastname: Ma
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China.|Ministry of Agriculture, Key Lab of Animal Bacteriology, Nanjing, 210095, China.
authors.forename: Min
authors.initials: M
authors.lastname: Sun
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China.|Ministry of Agriculture, Key Lab of Animal Bacteriology, Nanjing, 210095, China.
authors.forename: Wenyang
authors.initials: W
authors.lastname: Dong
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China.|Ministry of Agriculture, Key Lab of Animal Bacteriology, Nanjing, 210095, China.
authors.forename: Zihao
authors.initials: Z
authors.lastname: Pan
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China.|Ministry of Agriculture, Key Lab of Animal Bacteriology, Nanjing, 210095, China.
authors.forename: Chengping
authors.initials: C
authors.lastname: Lu
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China.|Ministry of Agriculture, Key Lab of Animal Bacteriology, Nanjing, 210095, China.
authors.forename: Huochun
authors.initials: H
authors.lastname: Yao
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000378:metabolism*; D001427:Bacterial Toxins / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018832:Molecular Chaperones / Q000378:metabolism; D000072417:Protein Domains; D000069376:Type VI Secretion Systems / Q000235:genetics / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001427:Bacterial Toxins; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D000069376:Type VI Secretion Systems