Structure and mechanism of the S component of a bacterial ECF transporter.
The energy-coupling factor (ECF) transporters, responsible for vitamin uptake in prokaryotes, are a unique family of membrane transporters. Each ECF transporter contains a membrane-embedded, substrate-binding protein (known as the S component), an energy-coupling module that comprises two ATP-binding proteins (known as the A and A' components) and a transmembrane protein (known as the T component). The structure and transport mechanism of the ECF family remain unknown. Here we report the crystal structure of RibU, the S component of the ECF-type riboflavin transporter from Staphylococcus aureus at 3.6-Å resolution. RibU contains six transmembrane segments, adopts a previously unreported transporter fold and contains a riboflavin molecule bound to the L1 loop and the periplasmic portion of transmembrane segments 4-6. Structural analysis reveals the essential ligand-binding residues, identifies the putative transport path and, with sequence alignment, uncovers conserved structural features and suggests potential mechanisms of action among the ECF transporters.
Zhang
Peng
P
Department of Molecular Biology, Lewis Thomas Laboratory, Princeton University, Princeton, New Jersey 08544, USA.
Wang
Jiawei
J
Shi
Yigong
Y
D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D008024:Ligands; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000145:classification / Q000378:metabolism*; D008958:Models, Molecular; D009068:Movement; D019897:Periplasm / Q000378:metabolism; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D012256:Riboflavin / Q000737:chemistry / Q000378:metabolism*; D016415:Sequence Alignment; D013211:Staphylococcus aureus / Q000737:chemistry*; D013379:Substrate Specificity
D001426:Bacterial Proteins; D008024:Ligands; D026901:Membrane Transport Proteins; D012256:Riboflavin