VgrG and PAAR Proteins Define Distinct Versions of a Functional Type VI Secretion System

• DOI: 10.1371/journal.ppat.1005735
• Publication Date: 2016-06-28T13:40:55Z
• Authors: Francesca R. Cian...; Juliana Alcoforad...; Manman Guo; Virginia De Cesare; Matthias Trost; Sarah J. Coulthurst
• Keywords: Proteomics; 0301 basic medicine; 570; QH301-705.5; Immunoblotting; 610; RC581-607; Type VI Secretion Systems; Chromatography, Affinity; Coculture Techniques; Mass Spectrometry; 03 medical and health sciences; Bacterial Proteins; Escherichia coli; Amino Acid Sequence; Immunologic diseases. Allergy; Biology (General); Serratia marcescens; Research Article

The Type VI secretion system (T6SS) is widespread among bacterial pathogens and acts as an effective weapon against competitor bacteria eukaryotic hosts by delivering toxic effector proteins directly into target cells. T6SS utilises a bacteriophage-like contractile machinery to expel puncturing device based on tube of Hcp topped with VgrG spike, which can be extended final tip from PAAR domain-containing protein. Effector are believed delivered specifically associating particular Hcp, or proteins, either covalently ('specialised') non-covalently ('cargo' effectors). Here we used the opportunistic pathogen Serratia marcescens, together integratecd genetic, proteomic biochemical approaches, elucidate role specific homologues in function specificity, revealing new aspects unexpected subtleties delivery T6SS. We identified effectors, both cargo specialised, absolutely dependent for cells, discovered that other effectors show preference VgrG. presence at least one protein was found essential function, consistent designation 'core' component. showed VgrG-PAAR combinations required assemble functional three distinct assemblies S. marcescens exhibit specificity efficiency. Unexpectedly, two different PAAR-containing Rhs functionally pair same Showing accessory EagR involved these interactions, native VgrG-Rhs-EagR complexes were isolated interactions between cognate identified. This study defines yet flexible highlights existence versions differential efficiency cell delivery.