Protein ProQ influences osmotic activation of compatible solute transporter ProP in Escherichia coli K-12

• Published in: Journal of bacteriology Vol. 181; no. 5; pp. 1537 - 1543
• Main Authors: Kunte, H J, Crane, R A, Culham, D E, Richmond, D, Wood, J M
• Format: Journal Article
• Language: English
• Published: United States American Society for Microbiology 01.03.1999
• Subjects: Amino Acid Sequence; Bacteria; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Carrier Proteins - chemistry; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cell Membrane - physiology; Chromosome Mapping; Conserved Sequence; DNA Transposable Elements; Escherichia coli; Escherichia coli - drug effects; Escherichia coli - genetics; Escherichia coli - physiology; Escherichia coli Proteins; Gene Expression Regulation, Bacterial; Membrane Transport Proteins; Microbiology; Molecular Sequence Data; Mutagenesis, Insertional; Osmolar Concentration; Physiology and Metabolism; Proline - metabolism; Recombinant Proteins - chemistry; Recombinant Proteins - metabolism; RNA-Binding Proteins; Sequence Alignment; Sequence Homology, Amino Acid; Sodium Chloride - pharmacology; Subcellular Fractions - metabolism; Symporters
• ISSN: 0021-9193; 1098-5530
• DOI: 10.1128/jb.181.5.1537-1543.1999

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.