Journal: Nat Microbiol / Year: 2020 Title: Structural and functional insights into oligopeptide acquisition by the RagAB transporter from Porphyromonas gingivalis. Authors: Mariusz Madej / Joshua B R White / Zuzanna Nowakowska / Shaun Rawson / Carsten Scavenius / Jan J Enghild / Grzegorz P Bereta / Karunakar Pothula / Ulrich Kleinekathoefer / Arnaud Baslé / ...Authors: Mariusz Madej / Joshua B R White / Zuzanna Nowakowska / Shaun Rawson / Carsten Scavenius / Jan J Enghild / Grzegorz P Bereta / Karunakar Pothula / Ulrich Kleinekathoefer / Arnaud Baslé / Neil A Ranson / Jan Potempa / Bert van den Berg / Abstract: Porphyromonas gingivalis, an asaccharolytic member of the Bacteroidetes, is a keystone pathogen in human periodontitis that may also contribute to the development of other chronic inflammatory ...Porphyromonas gingivalis, an asaccharolytic member of the Bacteroidetes, is a keystone pathogen in human periodontitis that may also contribute to the development of other chronic inflammatory diseases. P. gingivalis utilizes protease-generated peptides derived from extracellular proteins for growth, but how these peptides enter the cell is not clear. Here, we identify RagAB as the outer-membrane importer for these peptides. X-ray crystal structures show that the transporter forms a dimeric RagAB complex, with the RagB substrate-binding surface-anchored lipoprotein forming a closed lid on the RagA TonB-dependent transporter. Cryo-electron microscopy structures reveal the opening of the RagB lid and thus provide direct evidence for a 'pedal bin' mechanism of nutrient uptake. Together with mutagenesis, peptide-binding studies and RagAB peptidomics, our work identifies RagAB as a dynamic, selective outer-membrane oligopeptide-acquisition machine that is essential for the efficient utilization of proteinaceous nutrients by P. gingivalis.