---
res:
  bibo_abstract:
  - "Mrp (Multi resistance and pH adaptation) are broadly distributed secondary active
    antiporters that catalyze the transport of monovalent ions such as sodium and
    potassium outside of the cell coupled to the inward translocation of protons.
    Mrp antiporters are unique in a way that they are composed of seven subunits (MrpABCDEFG)
    encoded in a single operon, whereas other antiporters catalyzing the same reaction
    are mostly encoded by a single gene. Mrp exchangers are crucial for intracellular
    pH homeostasis and Na+ efflux, essential mechanisms for H+ uptake under alkaline
    environments and for reduction of the intracellular concentration of toxic cations.
    Mrp displays no homology to any other monovalent Na+(K+)/H+ antiporters but Mrp
    subunits have primary sequence similarity to essential redox-driven proton pumps,
    such as respiratory complex I and membrane-bound hydrogenases. This similarity
    reinforces the hypothesis that these present day redox-driven proton pumps are
    descended from the Mrp antiporter. The Mrp structure serves as a model to understand
    the yet obscure coupling mechanism between ion or electron transfer and proton
    translocation in this large group of proteins. In the thesis, I am presenting
    the purification, biochemical analysis, cryo-EM analysis and molecular structure
    of the Mrp complex from Anoxybacillus flavithermus solved by cryo-EM at 3.0 Å
    resolution. Numerous conditions were screened to purify Mrp to high homogeneity
    and to obtain an appropriate distribution of single particles on cryo-EM grids
    covered with a continuous layer of ultrathin carbon. A preferred particle orientation
    problem was solved by performing a tilted data collection. The activity assays
    showed the specific pH-dependent\r\nprofile of secondary active antiporters. The
    molecular structure shows that Mrp is a dimer of seven-subunit protomers with
    50 trans-membrane helices each. The dimer interface is built by many short and
    tilted transmembrane helices, probably causing a thinning of the bacterial membrane.
    The surface charge distribution shows an extraordinary asymmetry within each monomer,
    revealing presumable proton and sodium translocation pathways. The two largest\r\nand
    homologous Mrp subunits MrpA and MrpD probably translocate one proton each into
    the cell. The sodium ion is likely being translocated in the opposite direction
    within the small subunits along a ladder of charged and conserved residues. Based
    on the structure, we propose a mechanism were the antiport activity is accomplished
    via electrostatic interactions between the charged cations and key charged residues.
    The flexible key TM helices coordinate these\r\nelectrostatic interactions, while
    the membrane thinning between the monomers enables the translocation of sodium
    across the charged membrane. The entire family of redox-driven proton pumps is
    likely to perform their mechanism in a likewise manner.@eng"
  bibo_authorlist:
  - foaf_Person:
      foaf_givenName: Julia
      foaf_name: Steiner, Julia
      foaf_surname: Steiner
      foaf_workInfoHomepage: http://www.librecat.org/personId=3BB67EB0-F248-11E8-B48F-1D18A9856A87
    orcid: 0000-0003-0493-3775
  bibo_doi: 10.15479/AT:ISTA:8353
  dct_date: 2020^xs_gYear
  dct_isPartOf:
  - http://id.crossref.org/issn/2663-337X
  dct_language: eng
  dct_publisher: Institute of Science and Technology Austria@
  dct_title: Biochemical and structural investigation of the Mrp antiporter, an ancestor
    of complex I@
...