The structure of a tautomerase superfamily member linked to the type VI secretion system of Acinetobacter baumannii.
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ABSTRACT:
SUBMITTER: Pankov G
PROVIDER: S-EPMC9813972 | biostudies-literature | 2023 Jan
REPOSITORIES: biostudies-literature
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The structure of a tautomerase superfamily member linked to the type VI secretion system of Acinetobacter baumannii.
Pankov Genady G Mol Avelar Gabriela G Buchanan Grant G Coulthurst Sarah J SJ Hunter William N WN
Acta crystallographica. Section F, Structural biology communications 20230101 Pt 1
Bacteria exploit specialized secretion systems to assist in competition for resources, in collaboration and in communication. Here, a protocol for the recombinant production, purification and crystallization of a protein linked to the Acinetobacter baumannii type VI secretion system is provided. A high-resolution structure of this trimeric protein is reported, revealing the characteristic dual β-α-β subunit fold typical of longer subunit members of the tautomerase superfamily. The protein does n ...[more]
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Project description:In order to identify secreted proteins associated with the type VI secretion system (T6SS), the secretome of a wild-type A. baumannii AB307 0294 T6SS active strain was compared to the secretome of a T6SS inactive mutant strain, A. baumannii AB307-0294ΔtssM.
2018-05-25 | PXD009528 | Pride
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Project description:We investigated the genetic background and microbiological features of T6SS-positive Acinetobacter baumannii isolates and clinical impact of the T6SS in patients with A. baumannii bacteremia. One hundred and 62 A. baumannii isolates from patients with bacteremia in 2 tertiary-care hospitals in Korea were included in this study. Approximately one-third (51/162, 31.5%) of the A. baumannii clinical isolates possessed the hcp gene, and the hcp-positive isolates were found in several genotypes in multilocus sequence typing. The expression and secretion of Hcp protein varied among the clinical isolates. A. baumannii isolates with detectable Hcp secretion (T6SS+) could better outcompete Escherichia coli compared with T6SS- isolates, including hcp-negative and inactivated hcp-positive isolates. In addition, T6SS+ isolates showed higher biofilm-forming activity and better survival in the presence of normal human serum than the T6SS- isolates. T6SS+ isolates were more frequently detected in patients with catheter-related bloodstream infection, haematopoietic stem cell transplant recipients, and patients receiving immunosuppressive agents. However, T6SS was not a prognostic factor for mortality. Our results suggest that the T6SS of A. baumannii is associated with virulence and contributes to infections in immunocompromised patients and those with implanted medical devices.
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Project description:Acinetobacter baumannii is a Gram-negative opportunistic pathogen and is a common cause of nosocomial infections. The increasing development of antibiotic resistance in this organism is a global health concern. The A. baumannii clinical isolate AB307-0294 produces a type VI secretion system (T6SS) that delivers three antibacterial effector proteins that give this strain a competitive advantage against other bacteria in polymicrobial environments. Each effector, Tse15, Tde16, and Tae17, is delivered via a non-covalent interaction with a specific T6SS VgrG protein (VgrG15, VgrG16, and VgrG17, respectively). Here we define the regions of interaction between Tae17 and its cognate delivery protein VgrG17 and identify that amino acids G1069 and W1075 in VgrG17 are essential for Tae17 delivery via the T6SS, the first time such specific delivery determinants of T6SS cargo effectors have been defined. Furthermore, we determine that the Tae17 effector is a multidomain, bifunctional, peptidoglycan-degrading enzyme that has both amidase activity, which targets the sugar-peptide bonds, and lytic transglycosylase activity, which targets the peptidoglycan sugar backbone. Moreover, we show that the Tae17 transglycosylase activity is more important than amidase activity for the killing of Escherichia coli. This study provides molecular insight into how the T6SS allows A. baumannii strains to gain dominance in polymicrobial communities and thus improve their chances of survival and transmission.IMPORTANCEWe have shown that the Acinetobacter baumannii T6SS effector Tae17 is a modular, bifunctional, peptidoglycan-degrading enzyme that has both lytic transglycosylase and amidase activities. Both activities contribute to the ability to degrade peptidoglycan, but the transglycosylase activity was more important for the killing of Escherichia coli. We have defined the specific regions of Tae17 and its cognate delivery protein VgrG17 that are necessary for the non-covalent interactions and, for the first time, identified specific amino acids essential for T6SS cargo effector delivery. This work contributes to our molecular understanding of bacterial competition strategies in polymicrobial environments and may provide a window to design new therapeutic approaches for combating infection by A. baumannii.
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| S-EPMC10879597 | biostudies-literature
Project description:The type VI secretion system (T6SS) is a critical weapon in bacterial warfare between Gram-negative bacteria. Although invaluable for niche establishment, this machine represents an energetic burden to its host bacterium. Acinetobacter baumannii is an opportunistic pathogen that poses a serious threat to public health due to its high rates of multidrug resistance. In some A. baumannii strains, the T6SS is transcriptionally downregulated by large multidrug resistance plasmids. Other strains, such as the clinical isolate AbCAN2, express T6SS-related genes but lack T6SS activity under laboratory conditions, despite not harboring these plasmids. This suggests that alternative mechanisms exist to repress the T6SS. Here, we used a transposon mutagenesis approach in AbCAN2 to identify novel T6SS repressors. Our screen revealed that the T6SS of this strain is inhibited by a homolog of VgrG, an essential structural component of all T6SSs reported to date. We named this protein inhibitory VgrG (VgrGi). Biochemical and in silico analyses demonstrated that the unprecedented inhibitory capability of VgrGi is due to a single amino acid mutation in a widely conserved C-terminal domain of unknown function, DUF2345. We also show that unlike in other bacteria, the C terminus of VgrG is essential for functional T6SS assembly in A. baumannii Our study provides insight into the architectural requirements underlying functional assembly of the T6SS of A. baumannii We propose that T6SS-inactivating point mutations are beneficial to the host bacterium, since they eliminate the energy cost associated with maintaining a functional T6SS, which appears to be unnecessary for A. baumannii virulence.IMPORTANCE Despite the clinical relevance of A. baumannii, little is known about its fundamental biology. Here, we show that a single amino acid mutation in VgrG, a critical T6SS structural protein, abrogates T6SS function. Given that this mutation was found in a clinical isolate, we propose that the T6SS of A. baumannii is probably not involved in virulence; this idea is supported by multiple genomic analyses showing that the majority of clinical A. baumannii strains lack proteins essential to the T6SS. We also show that, unlike in other species, the C terminus of VgrG is a unique architectural requirement for functional T6SS assembly in A. baumannii, suggesting that over evolutionary time, bacteria have developed changes to their T6SS architecture, leading to specialized systems.
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