title: Structure of a pantothenate transporter and implications for ECF module sharing and energy coupling of group II ECF transporters.
abstract: Energy-coupling factor (ECF) transporters are a unique group of ATP-binding cassette (ABC) transporters responsible for micronutrient uptake from the environment. Each ECF transporter is composed of an S component (or EcfS protein) and T/A/A' components (or EcfT/A/A' proteins; ECF module). Among the group II ECF transporters, several EcfS proteins share one ECF module; however, the underlying mechanism remains unknown. Here we report the structure of a group II ECF transporter-pantothenate transporter from Lactobacillus brevis (LbECF-PanT), which shares the ECF module with the folate and hydroxymethylpyrimidine transporters (LbECF-FolT and LbECF-HmpT). Structural and mutational analyses revealed the residues constituting the pantothenate-binding pocket. We found that although the three EcfS proteins PanT, FolT, and HmpT are dissimilar in sequence, they share a common surface area composed of the transmembrane helices 1/2/6 (SM1/2/6) to interact with the coupling helices 2/3 (CH2/3) of the same EcfT. CH2 interacts mainly with SM1 via hydrophobic interactions, which may modulate the sliding movement of EcfS. CH3 binds to a hydrophobic surface groove formed by SM1, SM2, and SM6, which may transmit the conformational changes from EcfA/A' to EcfS. We also found that the residues at the intermolecular surfaces in LbECF-PanT are essential for transporter activity, and that these residues may mediate intermolecular conformational transmission and/or affect transporter complex stability. In addition, we found that the structure of EcfT is conformationally dynamic, which supports its function as a scaffold to mediate the interaction of the ECF module with various EcfS proteins to form different transporter complexes.
authors.affiliation: National Key Laboratory of Plant Molecular Genetics and.
authors.forename: Minhua
authors.initials: M
authors.lastname: Zhang
authors.affiliation: National Key Laboratory of Plant Molecular Genetics and Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
authors.forename: Zhihao
authors.initials: Z
authors.lastname: Bao
authors.affiliation: National Key Laboratory of Plant Molecular Genetics and.
authors.forename: Qin
authors.initials: Q
authors.lastname: Zhao
authors.affiliation: National Key Laboratory of Plant Molecular Genetics and.
authors.forename: Hui
authors.initials: H
authors.lastname: Guo
authors.affiliation: National Key Laboratory of Plant Molecular Genetics and.
authors.forename: Ke
authors.initials: K
authors.lastname: Xu
authors.affiliation: National Key Laboratory of Plant Molecular Genetics and.
authors.forename: Chengcheng
authors.initials: C
authors.lastname: Wang
authors.affiliation: National Key Laboratory of Plant Molecular Genetics and CAS Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, and pengzhang01@sibs.ac.cn.
authors.forename: Peng
authors.identifier: http://orcid.org/0000-0003-0408-2923
authors.initials: P
authors.lastname: Zhang
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D052196:Levilactobacillus brevis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D046912:Multiprotein Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D027981:Symporters / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D046912:Multiprotein Complexes; D027981:Symporters; C119982:pantothenate transporter
keywords: ATP-binding cassette transporter; ECF module; energy-coupling factor transporter; pantothenate transporter; transport mechanism