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.
Department of Molecular Biology, Lewis Thomas Laboratory, Princeton University, Princeton, New Jersey 08544, USA.
Peng
P
Zhang
Jiawei
J
Wang
Yigong
Y
Shi
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