title: Essential residues in the chromate transporter ChrA of Pseudomonas aeruginosa.
abstract: The chrA gene of Pseudomonas aeruginosa plasmid pUM505 encodes the hydrophobic protein ChrA, which confers resistance to chromate by the energy-dependent efflux of chromate ions. Chromate-sensitive mutants were isolated by in vivo random mutagenesis. Transport experiments with cell suspensions of selected mutants showed that 51CrO4(2-) extrusion was drastically lowered as compared to suspensions of the strain with the wild-type plasmid, confirming that the mutations affected a chromate efflux system. DNA sequence analysis showed that most point mutations affected amino acids clustered in the N-terminal half of ChrA, altering either cytoplasmic regions or transmembrane segments, and replaced residues moderately to highly conserved in ChrA homologs. PhoA and LacZ translational fusions were used to confirm the membrane topology at the N-terminal half of the ChrA protein.
authors.affiliation: Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana, Edificio B-3, Ciudad Universitaria, 58030 Morelia, Mich., Mexico.
authors.forename: Selene
authors.initials: S
authors.lastname: Aguilera
authors.forename: Ma Esther
authors.initials: ME
authors.lastname: Aguilar
authors.forename: Martha P
authors.initials: MP
authors.lastname: Chávez
authors.forename: Joel E
authors.initials: JE
authors.lastname: López-Meza
authors.forename: Mario
authors.initials: M
authors.lastname: Pedraza-Reyes
authors.forename: Jesús
authors.initials: J
authors.lastname: Campos-García
authors.forename: Carlos
authors.initials: C
authors.lastname: Cervantes
mesh_terms: D000595:Amino Acid Sequence; D019677:Artificial Gene Fusion; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D001693:Biological Transport, Active / Q000235:genetics; D002840:Chromates / Q000378:metabolism*; D004252:DNA Mutational Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000302:isolation & purification; D024881:Drug Resistance, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D017930:Genes, Reporter; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000502:physiology; D016296:Mutagenesis; D020125:Mutation, Missense; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism; D010957:Plasmids; D017433:Protein Structure, Secondary; D011550:Pseudomonas aeruginosa / Q000235:genetics* / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D002840:Chromates; D004269:DNA, Bacterial; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C073039:ChrA protein, Bacteria; D010744:Phosphoric Monoester Hydrolases; D001616:beta-Galactosidase