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Transmembrane helix 6b links proton and metal release pathways and drives conformational change in an Nramp-family transition metal transporter
- Source :
- J Biol Chem
- Publication Year :
- 2019
- Publisher :
- Elsevier BV, 2019.
-
Abstract
- The natural resistance-associated macrophage protein (Nramp) family encompasses transition metal and proton cotransporters that are present in many organisms from bacteria to humans. Recent structures of Deinococcus radiodurans Nramp (DraNramp) in multiple conformations revealed the intramolecular rearrangements required for alternating access of the metal-binding site to the external or cytosolic environment. Here, using recombinant proteins and metal transport and cysteine accessibility assays, we demonstrate that two parallel cytoplasm-accessible networks of conserved hydrophilic residues in DraNramp, one lining the wide intracellular vestibule for metal release and the other forming a narrow proton transport pathway, are essential for metal transport. We further show that mutagenic or posttranslational modifications of transmembrane helix (TM) 6b, which structurally links these two pathways, impede normal conformational cycling and metal transport. TM6b contains two highly conserved histidines, His232 and His237. We found that different mutagenic perturbations of His232, just below the metal-binding site along the proton exit route, differentially affect DraNramp's conformational state, suggesting that His232 serves as a pivot point for conformational changes. In contrast, any replacement of His237, lining the metal exit route, locked the transporter in a transport-inactive outward-closed state. We conclude that these two histidines, and TM6b more broadly, help trigger the bulk rearrangement of DraNramp to the inward-open state upon metal binding and facilitate return of the empty transporter to an outward-open state upon metal release.
- Subjects :
- Models, Molecular
Conformational change
Protein Conformation
Biochemistry
Membrane Biology
Proton transport
Histidine
Amino Acid Sequence
Cation Transport Proteins
Molecular Biology
Manganese
Ion Transport
biology
Chemistry
Deinococcus radiodurans
Transporter
Cobalt
Cell Biology
Membrane transport
biology.organism_classification
Transmembrane domain
Metals
Mutation
Biophysics
Deinococcus
Protons
Cotransporter
Hydrophobic and Hydrophilic Interactions
Protein Processing, Post-Translational
Cysteine
Subjects
Details
- ISSN :
- 1083351X and 00219258
- Volume :
- 295
- Database :
- OpenAIRE
- Journal :
- Journal of Biological Chemistry
- Accession number :
- edsair.doi.dedup.....e867766e8689b897aca78589484cca7f
- Full Text :
- https://doi.org/10.1074/jbc.ra119.011336