title: Methionine uptake in Corynebacterium glutamicum by MetQNI and by MetPS, a novel methionine and alanine importer of the NSS neurotransmitter transporter family.
abstract: The soil bacterium Corynebacterium glutamicum is a model organism in amino acid biotechnology. Here we present the identification of two different L-methionine uptake systems including the first characterization of a bacterial secondary methionine carrier. The primary carrier MetQNI is a high affinity ABC-type transporter specific for l-methionine. Its expression is under the control of the transcription factor McbR, the global regulator of sulfur metabolism in C. glutamicum. Besides MetQNI, a novel secondary methionine uptake system of the NSS (neurotransmitter:sodium symporter) family was identified and named MetP. The MetP system is characterized by a lower affinity for methionine and uses Na(+) ions for energetic coupling. It is also the main alanine transporter in C. glutamicum and is expressed constitutively. These observations are consistent with models of methionine, alanine, and leucine bound to MetP, derived from the X-ray crystal structure of the LeuT transporter from Aquifex aeolicus. Complementation studies show that MetP consists of two components, a large subunit with 12 predicted transmembrane segments and, surprisingly, an additional subunit with one predicted transmembrane segment only. Thus, this new member of the NSS transporter family adds a novel feature to this class of carriers, namely, the functional dependence on an additional small subunit.
authors.affiliation: Institute of Biochemistry, University of Koln, 50674 Koln, Germany, and Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt, Germany kay.marin@uni-koeln.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Trötschel
authors.forename: Martin
authors.initials: M
authors.lastname: Follmann
authors.forename: Jeannine A
authors.initials: JA
authors.lastname: Nettekoven
authors.forename: Tobias
authors.initials: T
authors.lastname: Mohrbach
authors.forename: Lucy R
authors.initials: LR
authors.lastname: Forrest
authors.forename: Andreas
authors.initials: A
authors.lastname: Burkovski
authors.forename: Kay
authors.initials: K
authors.lastname: Marin
authors.forename: Reinhard
authors.initials: R
authors.lastname: Krämer
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000409:Alanine / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001693:Biological Transport, Active; D048230:Corynebacterium glutamicum / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008715:Methionine / Q000378:metabolism*; D008958:Models, Molecular; D050479:Neurotransmitter Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D021122:Protein Subunits; D040681:Structural Homology, Protein
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D050479:Neurotransmitter Transport Proteins; D021122:Protein Subunits; D008715:Methionine; D000409:Alanine