title: Characterization of an iron-regulated alpha-enolase of Bacteroides fragilis.
abstract: This study describes the identification, cloning and molecular characterization of the alpha-enolase P46 of Bacteroides fragilis. The gram-negative anaerobic bacterium B. fragilis is a member of the commensal flora of the human intestine but is also frequently found in severe intra-abdominal infections. Several virulence factors have been described that may be involved in the development of these infections. Many of these virulence factors are upregulated under conditions of iron- or heme-starvation. We found a major protein of 46 kDa (P46) that is upregulated under iron-depleted conditions. This protein was identified as an alpha-enolase. Alpha-enolases in several gram-positive bacteria and eukaryotic cells are located at the cell surface and function as plasminogen-binding proteins. Localization studies demonstrated that P46 is mainly located in the cytoplasm and partly associated with the inner membrane (IM). Under iron-restricted conditions, however, P46 is localized primarily in the IM fraction. Plasminogen-binding to B. fragilis cells did occur but was not P46 dependent. A 60-kDa protein was identified as a putative plasminogen-binding protein in B. fragilis.
authors.affiliation: Department of Molecular Microbiology, Vrije Universiteit, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands.
authors.forename: Robert
authors.initials: R
authors.lastname: Sijbrandi
authors.forename: Tanneke
authors.initials: T
authors.lastname: Den Blaauwen
authors.forename: Jeremy R H
authors.initials: JR
authors.lastname: Tame
authors.forename: Bauke
authors.initials: B
authors.lastname: Oudega
authors.forename: Joen
authors.initials: J
authors.lastname: Luirink
authors.forename: Ben R
authors.initials: BR
authors.lastname: Otto
mesh_terms: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000032:analysis / Q000502:physiology; D001441:Bacteroides fragilis / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D002352:Carrier Proteins / Q000032:analysis; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D007425:Intracellular Membranes / Q000378:metabolism; D000090463:Iron Deficiencies; D033862:Iron-Binding Proteins; D008969:Molecular Sequence Data; D008970:Molecular Weight; D033902:Periplasmic Binding Proteins; D010751:Phosphopyruvate Hydratase / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D015854:Up-Regulation
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D033862:Iron-Binding Proteins; D033902:Periplasmic Binding Proteins; C084529:plasminogen-binding protein, bacteria; D010751:Phosphopyruvate Hydratase; C502005:alpha-enolase P46, Bacteroides fragilis