title: Novel MntR-independent mechanism of manganese homeostasis in Escherichia coli by the ribosome-associated protein HflX.
abstract: Manganese is a micronutrient required for activities of several important enzymes under conditions of oxidative stress and iron starvation. In Escherichia coli, the manganese homeostasis network primarily constitutes a manganese importer (MntH) and an exporter (MntP), which are regulated by the MntR dual regulator. In this study, we find that deletion of E. coli hflX, which encodes a ribosome-associated GTPase with unknown function, renders extreme manganese sensitivity characterized by arrested cell growth, filamentation, lower rate of replication, and DNA damage. We demonstrate that perturbation by manganese induces unprecedented influx of manganese in ΔhflX cells compared to that in the wild-type E. coli strain. Interestingly, our study indicates that the imbalance in manganese homeostasis in the ΔhflX strain is independent of the MntR regulon. Moreover, the influx of manganese leads to a simultaneous influx of zinc and inhibition of iron import in ΔhflX cells. In order to review a possible link of HflX with the λ phage life cycle, we performed a lysis-lysogeny assay to show that the Mn-perturbed ΔhflX strain reduces the frequency of lysogenization of the phage. This observation raises the possibility that the induced zinc influx in the manganese-perturbed ΔhflX strain stimulates the activity of the zinc-metalloprotease HflB, the key determinant of the lysis-lysogeny switch. Finally, we propose that manganese-mediated autophosphorylation of HflX plays a central role in manganese, zinc, and iron homeostasis in E. coli cells.
authors.affiliation: Laboratory of Molecular Biochemistry, CSIR-Institute of Microbial Technology, Chandigarh, India.
authors.forename: Gursharan
authors.initials: G
authors.lastname: Kaur
authors.affiliation: Department of Biochemistry, Bose Institute, Kolkata, India.
authors.forename: Sandeepan
authors.initials: S
authors.lastname: Sengupta
authors.affiliation: Laboratory of Molecular Biochemistry, CSIR-Institute of Microbial Technology, Chandigarh, India.
authors.forename: Vineet
authors.initials: V
authors.lastname: Kumar
authors.affiliation: Laboratory of Molecular Biochemistry, CSIR-Institute of Microbial Technology, Chandigarh, India.
authors.forename: Aruna
authors.initials: A
authors.lastname: Kumari
authors.affiliation: Department of Biochemistry, Bose Institute, Kolkata, India.
authors.forename: Aditi
authors.initials: A
authors.lastname: Ghosh
authors.affiliation: Department of Biochemistry, Bose Institute, Kolkata, India.
authors.forename: Pradeep
authors.initials: P
authors.lastname: Parrack
authors.affiliation: Laboratory of Molecular Biochemistry, CSIR-Institute of Microbial Technology, Chandigarh, India dutta@imtech.res.in.
authors.forename: Dipak
authors.initials: D
authors.lastname: Dutta
mesh_terms: D001692:Biological Transport / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D006706:Homeostasis / Q000502:physiology*; D008345:Manganese / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D029968:Escherichia coli Proteins; C499677:MntR protein, E coli; D012097:Repressor Proteins; D008345:Manganese; D019204:GTP-Binding Proteins; C535071:HflX protein, E coli