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Tn6553, a Tn7-family transposon encoding putative iron uptake functions found in Acinetobacter.

ABSTRACT: Acinetobacter baumannii is an opportunistic pathogen that has become difficult to eradicate mainly because of its high level of antibiotic resistance. Other features that contribute to this organism's success are the ability to compete for nutrients and iron. Recently, several novel Tn7-family transposons that encode synthesis and transport of siderophore and iron uptake systems were characterised. Here, another Tn7-type transposon (named Tn6553) is described. Tn6553 contains a set of iron utilisation genes with a transposition module related to Tn7. Tn7-family transposons that carry iron uptake systems facilitate the spread of these functions in Acinetobacter strains. Given that Tn7 is known to transpose efficiently into its preferred target site, finding siderophore functions on Tn7 family transposons is important in the context of dissemination of virulence genes amongst Acinetobacter strains.

SUBMITTER: Hamidian M

PROVIDER: S-EPMC9605922 | biostudies-literature | 2022 Oct

REPOSITORIES: biostudies-literature

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Tn6553, a Tn7-family transposon encoding putative iron uptake functions found in Acinetobacter.

Hamidian Mehrad M

Archives of microbiology 20221026 11

Acinetobacter baumannii is an opportunistic pathogen that has become difficult to eradicate mainly because of its high level of antibiotic resistance. Other features that contribute to this organism's success are the ability to compete for nutrients and iron. Recently, several novel Tn7-family transposons that encode synthesis and transport of siderophore and iron uptake systems were characterised. Here, another Tn7-type transposon (named Tn6553) is described. Tn6553 contains a set of iron utili ...[more]

PMID: 36289115

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Project description:Chemosensory pathways correspond to major signal transduction mechanisms and can be classified into the functional families flagellum-mediated taxis, type four pili-mediated taxis or pathways with alternative cellular functions (ACF). CheR methyltransferases are core enzymes in all of these families. CheR proteins fused to tetratricopeptide repeat (TPR) domains have been reported and we present an analysis of this uncharacterized family. We show that CheR-TPRs are widely distributed in GRAM-negative but almost absent from GRAM-positive bacteria. Most strains contain a single CheR-TPR and its abundance does not correlate with the number of chemoreceptors. The TPR domain fused to CheR is comparatively short and frequently composed of 2 repeats. The majority of CheR-TPR genes were found in gene clusters that harbor multidomain response regulators in which the REC domain is fused to different output domains like HK, GGDEF, EAL, HPT, AAA, PAS, GAF, additional REC, HTH, phosphatase or combinations thereof. The response regulator architectures coincide with those reported for the ACF family of pathways. Since the presence of multidomain response regulators is a distinctive feature of this pathway family, we conclude that CheR-TPR proteins form part of ACF type pathways. The diversity of response regulator output domains suggests that the ACF pathways form a superfamily which regroups many different regulatory mechanisms, in which all CheR-TPR proteins appear to participate. In the second part we characterize WspC of Pseudomonas putida, a representative example of CheR-TPR. The affinities of WspC-Pp for S-adenosylmethionine and S-adenosylhomocysteine were comparable to those of prototypal CheR, indicating that WspC-Pp activity is in analogy to prototypal CheRs controlled by product feed-back inhibition. The removal of the TPR domain did not impact significantly on the binding constants and consequently not on the product feed-back inhibition. WspC-Pp was found to be monomeric, which rules out a role of the TPR domain in self-association.

Project description:The MerR family of transcriptional regulators are dimeric proteins with an N-terminal helix-turn-helix DNA binding domain (DBD), followed by an antiparallel coiled-coil subunit interaction region, and usually by a C-terminal effector binding domain (EBD). This family is distinguished by the high amino acid similarity in the DBD and low similarity in the EBD, consistent with the role of this domain in each protein in sensing effector molecules. Most members of the family are activators, and act at promoters with long spacer regions and respond to the binding of inducers by distorting the promoter DNA to allow open complex formation and transcriptional activation. In MerR proteins the EBD contains a metal binding pocket formed by three cysteines. This Cys center characteristic of MerR regulators is primarily suited for metal binding and mediates activation of metal detoxification systems in bacteria. Over the last decade, it has become clear that the MerR family of regulators is more diverse than originally recognized. The availability of completed bacterial genome sequences has enabled the search for additional types of MerR-like regulators. We here present a novel MerR-like transcription factor lacking an EBD involved in iron uptake regulation (MliR) present in the marine bacterium Bizionia argentinensis (JUB59). An in silico analysis revealed that homologues of the MliR protein are widely distributed among different bacterial species. Deletion of the mliR gene led to decreased cell growth, increased cell adhesion and filamentation. RNA sequencing analysis showed that expression of several iron uptake-related mRNAs were downregulated in mliR-deletion mutant. Through NMR-based metabolomics, ICP-MS, fluorescence microscopy and biochemical analysis we evaluated metabolic and phenotypic changes associated with mliR deletion. This work provides the first evidence of a MerR-family regulator involved in iron uptake and contributes to expanding our current knowledge on iron metabolism.in bacteria.

Dataset Information

Tn6553, a Tn7-family transposon encoding putative iron uptake functions found in Acinetobacter.

Publications

Tn6553, a Tn7-family transposon encoding putative iron uptake functions found in Acinetobacter.

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