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Gene Review

proP  -  proline/glycine betaine transporter

Escherichia coli str. K-12 substr. MG1655

Synonyms: ECK4104, JW4072
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Disease relevance of proP

  • E. coli gene proP was isolated and located within a chromosomal DNA fragment [1].
  • The slow growth of both pyelonephritis isolates in high-osmolality medium was stimulated by glycine betaine (GB) and deletion of proP and/or proU impaired GB uptake [2].

High impact information on proP

  • Two full-length transporters could complement the Na(+)-sensitive phenotype of the Escherichia coli mutant deficient in betT, putPA, proP, and proU [3].
  • That activity was: (i) dependent on the presence of the energy sources phenazine methosulphate plus ascorbate or D-lactate; (ii) observed only when a hyperosmotic shift accompanied the transport measurement; (iii) inhibited by glycine betaine in a manner analogous to that observed in whole cells; and (iv) eliminated by lesions in proP [4].
  • The mRNA level of two genes was more than fivefold decreased in the mutant, i.e. betP and proP which encode transporters for the uptake of betaine and proline respectively [5].
  • Transporters encoded in genetic loci putP, proP and proU mediate proline and/or betaine accumulation by Escherichia coli K-12 [1].
  • Isolation and sequencing of Escherichia coli gene proP reveals unusual structural features of the osmoregulatory proline/betaine transporter, ProP [1].

Chemical compound and disease context of proP

  • Under these conditions, an E. coli K-12 strain with lesions in both proP and proU accumulates low levels of L-carnitine but fails to accumulate betaine when these compounds are supplied in the external medium [6].
  • Morpholinopropane sulfonic acid, a common constituent of microbiological media, accumulates in osmoadapting E. coli cells but it is not osmoprotective and it did not influence proP transcription or ProP activity [7].

Biological context of proP


Anatomical context of proP

  • Deletion of proP and proU slowed the growth of E. coli HU734 in this high-osmolality human urine (which contains betaines) but had little impact on its colonization of the murine urinary tract after transurethral inoculation [2].

Associations of proP with chemical compounds

  • In vitro expression of proP yielded a protein whose apparent molecular mass was determined to be 42 kDa by polyacrylamide gel electrophoresis under denaturing conditions [1].
  • Protein purification was facilitated by the addition of six histidine (His) codons to the 3' end of proP [9].
  • An HU734 derivative lacking both proP and proU retained osmoprotective GB uptake activity that could be attributed to system BetU, which is not present in strain K-12 or CFT073 [2].
  • We find that proP, which encodes a low-affinity transporter of the important osmoprotectants proline and glycine betaine, is transcribed from two promoters. proP1 is transiently induced upon subculture and is upregulated by increases in medium osmolarity [10].

Other interactions of proP

  • By contrast, deletion of rpoS, proP and proU had no effect on the very rapid growth of CFT073 in high-osmolality urine or on its experimental colonization of the murine urinary tract [2].
  • In the presence of Fis, proP2 expression is increased over 50-fold, as judged by the LacZ activity of cells carrying the proP-lacZ fusion as well as by direct RNA analysis, making this the most strongly activated promoter by Fis that has been described [10].


  1. Isolation and sequencing of Escherichia coli gene proP reveals unusual structural features of the osmoregulatory proline/betaine transporter, ProP. Culham, D.E., Lasby, B., Marangoni, A.G., Milner, J.L., Steer, B.A., van Nues, R.W., Wood, J.M. J. Mol. Biol. (1993) [Pubmed]
  2. The osmotic stress response and virulence in pyelonephritis isolates of Escherichia coli: contributions of RpoS, ProP, ProU and other systems. Culham, D.E., Lu, A., Jishage, M., Krogfelt, K.A., Ishihama, A., Wood, J.M. Microbiology (Reading, Engl.) (2001) [Pubmed]
  3. Functional characterization of betaine/proline transporters in betaine-accumulating mangrove. Waditee, R., Hibino, T., Tanaka, Y., Nakamura, T., Incharoensakdi, A., Hayakawa, S., Suzuki, S., Futsuhara, Y., Kawamitsu, Y., Takabe, T., Takabe, T. J. Biol. Chem. (2002) [Pubmed]
  4. Proline porter II is activated by a hyperosmotic shift in both whole cells and membrane vesicles of Escherichia coli K12. Milner, J.L., Grothe, S., Wood, J.M. J. Biol. Chem. (1988) [Pubmed]
  5. Deletion of the genes encoding the MtrA-MtrB two-component system of Corynebacterium glutamicum has a strong influence on cell morphology, antibiotics susceptibility and expression of genes involved in osmoprotection. Möker, N., Brocker, M., Schaffer, S., Krämer, R., Morbach, S., Bott, M. Mol. Microbiol. (2004) [Pubmed]
  6. A possible role of ProP, ProU and CaiT in osmoprotection of Escherichia coli by carnitine. Verheul, A., Wouters, J.A., Rombouts, F.M., Abee, T. J. Appl. Microbiol. (1998) [Pubmed]
  7. The ion coupling and organic substrate specificities of osmoregulatory transporter ProP in Escherichia coli. MacMillan, S.V., Alexander, D.A., Culham, D.E., Kunte, H.J., Marshall, E.V., Rochon, D., Wood, J.M. Biochim. Biophys. Acta (1999) [Pubmed]
  8. Identification and characterization of the locus for diffuse adherence, which encodes a novel afimbrial adhesin found in atypical enteropathogenic Escherichia coli. Scaletsky, I.C., Michalski, J., Torres, A.G., Dulguer, M.V., Kaper, J.B. Infect. Immun. (2005) [Pubmed]
  9. Purification and reconstitution of an osmosensor: transporter ProP of Escherichia coli senses and responds to osmotic shifts. Racher, K.I., Voegele, R.T., Marshall, E.V., Culham, D.E., Wood, J.M., Jung, H., Bacon, M., Cairns, M.T., Ferguson, S.M., Liang, W.J., Henderson, P.J., White, G., Hallett, F.R. Biochemistry (1999) [Pubmed]
  10. Fis activates the RpoS-dependent stationary-phase expression of proP in Escherichia coli. Xu, J., Johnson, R.C. J. Bacteriol. (1995) [Pubmed]
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