title: Pyridoxamine is a substrate of the energy-coupling factor transporter HmpT.
abstract: Energy-coupling factor (ECF) transporters belong to a novel family of proteins that forms a subset within the ATP-binding cassette (ABC) transporter family. These proteins are responsible for the uptake of micronutrients in bacteria. ECF transporters are composed of four proteins: the A- and A'-components, the T-component and the S-component. One of the ECF transporters, named HmpT, was crystallized in the apo form with all four components. It is currently unknown whether HmpT serves as a transporter for hydroxymethyl pyrimidine or the different forms of vitamin B6 (pyridoxine, pyridoxal or pyridoxamine). Using a combination of molecular dynamics (MD) simulations and mass spectrometry, we have identified pyridoxamine to be the preferred substrate of HmpT. Mass spectra show that the mass of the substrate from the HmpT-substrate complex matches that of pyridoxamine. MD simulations likewise indicate that pyridoxamine interacts most strongly with most of the conserved residues of the S-component (Glu 41, His 84 and Gln 43) compared with the other vitamin B6 forms. Furthermore, the simulations have implied that loops 1 and 5 of the S-component can participate in the gating action for HmpT.
authors.affiliation: Ministry of Education Key Laboratory of Protein Science, Tsinghua University, Beijing, China; Tsinghua-Peking Joint Center for Life Sciences, Center for Structural Biology, School of Life Sciences and School of Medicine, Tsinghua University, Beijing, China.
authors.forename: Tingliang
authors.initials: T
authors.lastname: Wang
authors.affiliation: Department of Chemistry & Biochemistry, the BioFrontiers Institute, University of Colorado Boulder , Boulder, CO, USA.
authors.forename: Armando Jerome
authors.initials: AJ
authors.lastname: de Jesus
authors.affiliation: Ministry of Education Key Laboratory of Protein Science, Tsinghua University, Beijing, China; Tsinghua-Peking Joint Center for Life Sciences, Center for Structural Biology, School of Life Sciences and School of Medicine, Tsinghua University, Beijing, China.
authors.forename: Yigong
authors.initials: Y
authors.lastname: Shi
authors.affiliation: Department of Chemistry & Biochemistry, the BioFrontiers Institute, University of Colorado Boulder, Boulder, CO, USA; Center of Basic Molecular Science, Department of Chemistry, Tsinghua University, Beijing, China.
authors.forename: Hang
authors.identifier: 0000-0002-9762-4818
authors.initials: H
authors.lastname: Yin
keywords: ECF transporters; HmpT; S-component; gating mechanism; mass spectrometry; molecular dynamics