title: An essential role for actA in acid tolerance of Rhizobium meliloti.
abstract: The actA gene, which is disrupted by Tn5 in the acid-sensitive mutant of Rhizobium meliloti TG2-6, was cloned and sequenced. It encodes a protein of 541 amino acids with a calculated molecular mass of 57,963 Da and an estimated pl of 9.0. The ActA protein sequence has 30% identity, and much higher similarity (69%), with the CutE protein of Escherichia coli. Like the cutE mutant of E. coli, TG2-6 is sensitive to copper. The reconstructed wild-type actA gene complemented the low pH- and copper-sensitive phenotype of TG2-6. Studies with an actA-lacZ gene fusion showed that actA is constitutively expressed at pH 5.8 and 7.0. The actA gene appears to be chromosomal and is present in all seven strains of R. meliloti tested.
authors.affiliation: Nitrogen Fixation Research Group, School of Biological and Environmental Sciences, Murdoch University, Murdoch, Western Australia 6150.
authors.forename: Ravi P
authors.initials: RP
authors.lastname: Tiwari
authors.affiliation: Nitrogen Fixation Research Group, School of Biological and Environmental Sciences, Murdoch University, Murdoch, Western Australia 6150.
authors.forename: Wayne G
authors.initials: WG
authors.lastname: Reeve
authors.affiliation: Nitrogen Fixation Research Group, School of Biological and Environmental Sciences, Murdoch University, Murdoch, Western Australia 6150.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Dilworthan
authors.affiliation: Nitrogen Fixation Research Group, School of Biological and Environmental Sciences, Murdoch University, Murdoch, Western Australia 6150.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Glenn
mesh_terms: D000123:Acetyltransferases; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D016415:Sequence Alignment; D017421:Sequence Analysis; D016962:Sinorhizobium meliloti / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C072980:actA protein, Listeria monocytogenes; D000123:Acetyltransferases; C071443:cutE protein, E coli