title: Dissecting the Molecular Mechanism of Nucleotide-Dependent Activation of the KtrAB K+ Transporter.
abstract: KtrAB belongs to the Trk/Ktr/HKT superfamily of monovalent cation (K+ and Na+) transport proteins that closely resemble K+ channels. These proteins underlie a plethora of cellular functions that are crucial for environmental adaptation in plants, fungi, archaea, and bacteria. The activation mechanism of the Trk/Ktr/HKT proteins remains unknown. It has been shown that ATP stimulates the activity of KtrAB while ADP does not. Here, we present X-ray structural information on the KtrAB complex with bound ADP. A comparison with the KtrAB-ATP structure reveals conformational changes in the ring and in the membrane protein. In combination with a biochemical and functional analysis, we uncover how ligand-dependent changes in the KtrA ring are propagated to the KtrB membrane protein and conclude that, despite their structural similarity, the activation mechanism of KtrAB is markedly different from the activation mechanism of K+ channels.
authors.affiliation: IBMC, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.
authors.forename: Andras
authors.initials: A
authors.lastname: Szollosi
authors.affiliation: IBMC, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.
authors.forename: Ricardo S
authors.initials: RS
authors.lastname: Vieira-Pires
authors.affiliation: IBMC, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.|Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.
authors.forename: Celso M
authors.initials: CM
authors.lastname: Teixeira-Duarte
authors.affiliation: IBMC, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.|Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.
authors.forename: Rita
authors.initials: R
authors.lastname: Rocha
authors.affiliation: IBMC, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.|Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.
authors.forename: João H
authors.initials: JH
authors.lastname: Morais-Cabral
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D001412:Bacillus subtilis / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli; D011188:Potassium / Q000378:metabolism*; D011487:Protein Conformation
chemical_list: D001426:Bacterial Proteins; D027682:Cation Transport Proteins; C113206:KtrB protein, Bacteria; D000255:Adenosine Triphosphate; D011188:Potassium