Bacterial metal detectors.
Gram negative bacteria can detect environmental iron using outer membrane transporters (OMTs), and then regulate certain transport genes to take advantage of a readily available iron source. This process begins with an iron complex being bound by an OMT, and results in a signal being sent across the outer membrane, the periplasmic space, and the inner membrane, to a sigma factor that interacts with RNA polymerase and initiates transcription of relevant genes. Many of the interactions contributing to signalling have been observed by genetic and biochemical studies, but structural studies, which potentially show these interactions in molecular detail, have been limited. In this issue, Garcia-Herrero and Vogel describe an NMR structure of the periplasmic domain of an OMT, which had not been seen in previous X-ray crystal structures. This domain transmits the 'iron availability' signal to the next protein in the signal transduction cascade, which sits in the inner membrane and extends into the periplasm. The new structure extends our knowledge of transporter architecture and suggests how signalling may occur across the outer membrane.
Buchanan
Susan K
SK
Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA. skbuchan@helix.nih.gov
D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006090:Gram-Negative Bacteria / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D008565:Membrane Proteins; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D017262:Siderophores / Q000378:metabolism; D012808:Sigma Factor / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C028589:FecA protein, E coli; C093541:FecR protein, E coli; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D011956:Receptors, Cell Surface; D012097:Repressor Proteins; D017262:Siderophores; D012808:Sigma Factor; C068477:ferric uptake regulating proteins, bacterial; C057616:tonB protein, Bacteria; D007501:Iron