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| Title | Structural basis for the alternating access mechanism of the cation diffusion facilitator YiiP. |
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| Journal, issue, pages | Proc Natl Acad Sci U S A, Vol. 115, Issue 12, Page 3042-3047, Year 2018 |
| Publish date | Mar 20, 2018 |
 Authors | Maria Luisa Lopez-Redondo / Nicolas Coudray / Zhening Zhang / John Alexopoulos / David L Stokes /  |
| PubMed Abstract | YiiP is a dimeric antiporter from the cation diffusion facilitator family that uses the proton motive force to transport Zn across bacterial membranes. Previous work defined the atomic structure of ...YiiP is a dimeric antiporter from the cation diffusion facilitator family that uses the proton motive force to transport Zn across bacterial membranes. Previous work defined the atomic structure of an outward-facing conformation, the location of several Zn binding sites, and hydrophobic residues that appear to control access to the transport sites from the cytoplasm. A low-resolution cryo-EM structure revealed changes within the membrane domain that were associated with the alternating access mechanism for transport. In the current work, the resolution of this cryo-EM structure has been extended to 4.1 Å. Comparison with the X-ray structure defines the differences between inward-facing and outward-facing conformations at an atomic level. These differences include rocking and twisting of a four-helix bundle that harbors the Zn transport site and controls its accessibility within each monomer. As previously noted, membrane domains are closely associated in the dimeric structure from cryo-EM but dramatically splayed apart in the X-ray structure. Cysteine crosslinking was used to constrain these membrane domains and to show that this large-scale splaying was not necessary for transport activity. Furthermore, dimer stability was not compromised by mutagenesis of elements in the cytoplasmic domain, suggesting that the extensive interface between membrane domains is a strong determinant of dimerization. As with other secondary transporters, this interface could provide a stable scaffold for movements of the four-helix bundle that confers alternating access of these ions to opposite sides of the membrane. |
 External links | Proc Natl Acad Sci U S A / PubMed:29507252 / PubMed Central |
| Methods | EM (helical sym.) |
| Resolution | 4.1 Å |
| Structure data | |
| Chemicals |  ChemComp-ZN: |
| Source |
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 Keywords | MEMBRANE PROTEIN / zinc antiporter / cation diffusion facilitator / metal transport / helical crystals / Structural Genomics / PSI-Biology / Transcontinental EM Initiative for Membrane Protein Structure / TEMIMPS |
shewanella oneidensis mr-1 (bacteria)