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Nramp: from sequence to structure and mechanism of divalent metal import

Mathieu F M Cellier1

  • 1Institut National de la Research Scientifique-Institut Armand-Frappier, Laval, QC, Canada. mathieu.cellier@iaf.inrs.ca

Current Topics in Membranes
|October 11, 2012
PubMed

Insights

Natural resistance-associated macrophage proteins (Nramps) import essential metals like manganese and iron. Understanding Nramp structure and function is crucial for cellular homeostasis and preventing diseases linked to metal transport defects.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Genetics

Background:

  • Manganese (Mn) and iron (Fe) are vital for cellular energy metabolism and oxidative stress resistance.
  • The natural resistance-associated macrophage protein (Nramp) family facilitates proton and divalent metal import across cell membranes.
  • Nramps are conserved across species, from bacteria to humans, highlighting their fundamental biological role.

Purpose of the Study:

  • To elucidate the structural and functional characteristics of the Nramp family of metal transporters.
  • To investigate the evolutionary relationships and sequence features of Nramps and related transporters.
  • To explore the regulatory mechanisms and pathological implications of Nramp-mediated metal transport.

Main Methods:

  • Molecular phylogeny and sequence analysis to determine evolutionary relationships.
  • Structural modeling (3D) and experimental validation using transmembrane topology and structure-function studies.
  • Analysis of genetic data and conservation patterns in bacterial MntH transporters.
  • Investigation of eukaryotic Nramp regulation, including gene expression and protein trafficking.

Main Results:

  • Nramp hydrophobic core shares structural similarities with cation-driven carriers, supporting a pseudo-symmetric 3D model.
  • Phylogenetic analysis suggests remote ancestry to the LeuT superfamily and conserved sequence marks related to metal selectivity.
  • Bacterial MntH transporters exhibit conserved patterns linked to ecological distribution and potential virulence.
  • Experimental studies confirm the 3D model and highlight the role of Nramps in Mn and Fe homeostasis in eukaryotes.

Conclusions:

  • Nramps play a critical role in maintaining manganese and iron homeostasis in both prokaryotes and eukaryotes.
  • Dysfunctional Nramp transport is implicated in various human pathologies, including iron overload, neurodegenerative diseases, and infectious disease susceptibility.
  • Elaborate regulatory mechanisms control Nramp activity, impacting cellular and systemic metal traffic and signaling.

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