title: Substrate-induced conformational changes in the S-component ThiT from an energy coupling factor transporter.
abstract: Energy coupling factor (ECF) transporters are a recently discovered class of ABC transporters that mediate vitamin uptake in prokaryotes. Characteristic for ECF-type ABC transporters are small integral membrane proteins (S-components) that bind the transported substrates with high affinity. S-components associate with a second membrane protein (EcfT) and two peripheral ATPases to form a complete ATP-dependent transporter. Here, we have used EPR spectroscopy, stopped-flow fluorescence spectroscopy, and molecular dynamics simulations to determine the structural rearrangements that take place in the S-component ThiT from Lactococcus lactis upon binding of thiamin. Thiamin-induced conformational changes were confined to the long and partially membrane-embedded loop between transmembrane helices 1 and 2 that acts as a lid to occlude the binding site. The results indicate that solitary ThiT functions as a bona fide high-affinity substrate binding protein, which lacks a translocation pathway within the protein.
authors.affiliation: Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, Netherlands Proteomics Centre and Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
authors.forename: Maria
authors.initials: M
authors.lastname: Majsnerowska
authors.forename: Inga
authors.initials: I
authors.lastname: Hänelt
authors.forename: Dorith
authors.initials: D
authors.lastname: Wunnicke
authors.forename: Lars V
authors.initials: LV
authors.lastname: Schäfer
authors.forename: Heinz-Jürgen
authors.initials: HJ
authors.lastname: Steinhoff
authors.forename: Dirk Jan
authors.initials: DJ
authors.lastname: Slotboom
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D013294:Lactococcus lactis / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D013050:Spectrometry, Fluorescence; D013831:Thiamine / Q000737:chemistry / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D008565:Membrane Proteins; D013831:Thiamine