title: The role of trimerization in the osmoregulated betaine transporter BetP.
abstract: The osmoregulated betaine transporter BetP is a stable trimer. Structural studies have shown that individual protomers can adopt distinct transport conformations, implying a functional role for the trimeric state in transport, although the role of trimerization in regulation is not yet understood. We designed putative monomeric mutants by molecular-dynamics simulations and in silico alanine-scanning mutagenesis. Several mutants including BetP-W101A/T351A were monomeric in detergent as well as in the membrane, as shown by blue native gel electrophoresis, crosslinking and electron microscopy. This monomeric form retains the ability to accumulate betaine, but is no longer regulated by hyperosmotic shock.
authors.affiliation: Department of Structural Biology, Max-Planck Institute of Biophysics, Frankfurt am Main 60438, Germany.
authors.forename: Camilo
authors.initials: C
authors.lastname: Perez
authors.forename: Kamil
authors.initials: K
authors.lastname: Khafizov
authors.forename: Lucy R
authors.initials: LR
authors.lastname: Forrest
authors.forename: Reinhard
authors.initials: R
authors.lastname: Krämer
authors.forename: Christine
authors.initials: C
authors.lastname: Ziegler
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001622:Betaine / Q000378:metabolism*; D001692:Biological Transport; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D050485:GABA Plasma Membrane Transport Proteins; D008958:Models, Molecular; D009154:Mutation; D055503:Protein Multimerization; D021122:Protein Subunits / Q000737:chemistry; D011510:Proteolipids / Q000378:metabolism; D013329:Structure-Activity Relationship; D027981:Symporters; D014057:Tomography, X-Ray Computed / Q000379:methods; D014882:Water-Electrolyte Balance
chemical_list: D001426:Bacterial Proteins; C101652:BetP protein, Corynebacterium glutamicum; D002352:Carrier Proteins; D050485:GABA Plasma Membrane Transport Proteins; D021122:Protein Subunits; D011510:Proteolipids; D027981:Symporters; C020485:proteoliposomes; C072207:betaine plasma membrane transport proteins; D001622:Betaine