title: Identification of an iron-regulated, hemin-binding outer membrane protein in Sinorhizobium meliloti.
abstract: Rhizobia are soil bacteria that are able to establish symbiotic associations with leguminous hosts. In iron-limited environments these bacteria can use iron present in heme or heme compounds (hemoglobin, leghemoglobin). Here we report the presence in Sinorhizobium meliloti of an iron-regulated outer membrane protein that is able to bind hemin but not hemoglobin. Protein assignment was done by matrix-assisted laser desorption ionization-time of flight mass spectrometry. Tryptic peptides correlated with the mass measurements obtained accounted for 54% of the translated sequence of a putative heme receptor gene present in the chromosome of S. meliloti 1021. The results which we obtained suggest that this protein (designated ShmR for Sinorhizobium heme receptor) is involved in high-affinity heme-mediated iron transport.
authors.affiliation: Laboratorio de Ecología Microbiana. Unidad de Bioquímica Analítica, Instituto de Investigaciones Biológicas Clemente Estable (IIBCE-MEC), Montevideo 11600, Uruguay.
authors.forename: Federico
authors.initials: F
authors.lastname: Battistoni
authors.forename: Raúl
authors.initials: R
authors.lastname: Platero
authors.forename: Rosario
authors.initials: R
authors.lastname: Duran
authors.forename: Carlos
authors.initials: C
authors.lastname: Cerveñansky
authors.forename: Julio
authors.initials: J
authors.lastname: Battistoni
authors.forename: Alicia
authors.initials: A
authors.lastname: Arias
authors.forename: Elena
authors.initials: E
authors.lastname: Fabiano
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D002352:Carrier Proteins; D006418:Heme / Q000378:metabolism; D006427:Hemin / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D016962:Sinorhizobium meliloti / Q000737:chemistry* / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; C093956:HasA protein, Serratia marcescens; D008565:Membrane Proteins; D006418:Heme; D006427:Hemin; D007501:Iron