Protein ProQ influences osmotic activation of compatible solute transporter ProP in Escherichia coli K-12.
ProP is an osmoregulatory compatible solute transporter in Escherichia coli K-12. Mutation proQ220::Tn5 decreased the rate constant for and the extent of ProP activation by an osmotic upshift but did not alter proP transcription or the ProP protein level. Allele proQ220::Tn5 was isolated, and the proQ sequence was determined. Locus proQ is upstream from prc (tsp) at 41.2 centisomes on the genetic map. The proQ220::Tn5 and prc phenotypes were different, however. Gene proQ is predicted to encode a 232-amino-acid, basic, hydrophilic protein (molecular mass, 25,876 Da; calculated isoelectric point, 9.66; 32% D, E, R, or K; 54.5% polar amino acids). The insertion of PCR-amplified proQ into vector pBAD24 produced a plasmid containing the wild-type proQ open reading frame, the expression of which yielded a soluble protein with an apparent molecular mass of 30 kDa. Antibodies raised against the overexpressed ProQ protein detected cross-reactive material in proQ+ bacteria but not in proQ220::Tn5 bacteria. ProQ may be a structural element that influences the osmotic activation of ProP at a posttranslational level.
Department of Microbiology, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
H J
HJ
Kunte
R A
RA
Crane
D E
DE
Culham
D
D
Richmond
J M
JM
Wood
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002462:Cell Membrane / Q000502:physiology; D002874:Chromosome Mapping; D017124:Conserved Sequence; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009994:Osmolar Concentration; D011392:Proline / Q000378:metabolism; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012965:Sodium Chloride / Q000494:pharmacology; D013347:Subcellular Fractions / Q000378:metabolism; D027981:Symporters
D001426:Bacterial Proteins; D002352:Carrier Proteins; D004251:DNA Transposable Elements; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; C079244:ProP protein, E coli; C118132:ProQ protein, E coli; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D027981:Symporters; D012965:Sodium Chloride; D011392:Proline