Skip to main content
PMC home page
Journal of Bacteriology logoLink to Journal of Bacteriology
. 1992 Sep;174(17):5661–5668. doi: 10.1128/jb.174.17.5661-5668.1992

Enhanced export of beta-galactosidase fusion proteins in prlF mutants is Lon dependent.

W B Snyder 1, T J Silhavy 1
PMCID: PMC206513  PMID: 1512198

Abstract

We have used fusions of the outer membrane protein LamB to beta-galactosidase (encoded by lacZ) to study the protein export process. This LamB-LacZ hybrid protein blocks export when synthesized at high levels, as evidenced by inducer (maltose) sensitivity, a phenomenon termed LacZ hybrid jamming. The prlF1 mutation relieves LacZ hybrid jamming and allows localization of the fusion protein to a noncytoplasmic compartment. prlF1 and similar alleles are gain-of-function mutations. Null mutations in this gene confer no obvious phenotypes. Extragenic suppressors of a gain-of-function prlF allele have been isolated in order to understand how this gene product affects the export process. The suppressors are all lon null mutations, and they are epistatic to all prlF phenotypes tested. Lon protease activity has been measured in prlF1 cells and shown to be increased. However, the synthesis of Lon is not increased in a prlF1 background, suggesting a previously unidentified mechanism of Lon activation. Further analysis reveals that prlF1 activates degradation of cytoplasmically localized precursors in a Lon protease-dependent manner. It is proposed that accumulation of precursors during conditions of hybrid protein jamming titrates an essential export component(s), possibly a chaperone. Increased Lon-dependent precursor degradation would free this component, thus allowing increased protein export under jamming conditions.

Full text

PDF
5664

Images in this article

5664Image
on p.5664
5666Image
on p.5666
5666Image
on p.5666
5666Image
on p.5666

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Altman E., Bankaitis V. A., Emr S. D. Characterization of a region in mature LamB protein that interacts with a component of the export machinery of Escherichia coli. J Biol Chem. 1990 Oct 25;265(30):18148–18153. [PubMed] [Google Scholar]
  2. Baird L., Georgopoulos C. Identification, cloning, and characterization of the Escherichia coli sohA gene, a suppressor of the htrA (degP) null phenotype. J Bacteriol. 1990 Mar;172(3):1587–1594. doi: 10.1128/jb.172.3.1587-1594.1990. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Baird L., Lipinska B., Raina S., Georgopoulos C. Identification of the Escherichia coli sohB gene, a multicopy suppressor of the HtrA (DegP) null phenotype. J Bacteriol. 1991 Sep;173(18):5763–5770. doi: 10.1128/jb.173.18.5763-5770.1991. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Bankaitis V. A., Bassford P. J., Jr The synthesis of export-defective proteins can interfere with normal protein export in Escherichia coli. J Biol Chem. 1984 Oct 10;259(19):12193–12200. [PubMed] [Google Scholar]
  5. Bieker K. L., Phillips G. J., Silhavy T. J. The sec and prl genes of Escherichia coli. J Bioenerg Biomembr. 1990 Jun;22(3):291–310. doi: 10.1007/BF00763169. [DOI] [PubMed] [Google Scholar]
  6. Bieker K. L., Silhavy T. J. PrlA (SecY) and PrlG (SecE) interact directly and function sequentially during protein translocation in E. coli. Cell. 1990 Jun 1;61(5):833–842. doi: 10.1016/0092-8674(90)90193-i. [DOI] [PubMed] [Google Scholar]
  7. Goff S. A., Casson L. P., Goldberg A. L. Heat shock regulatory gene htpR influences rates of protein degradation and expression of the lon gene in Escherichia coli. Proc Natl Acad Sci U S A. 1984 Nov;81(21):6647–6651. doi: 10.1073/pnas.81.21.6647. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Gottesman S. Genetics of proteolysis in Escherichia coli*. Annu Rev Genet. 1989;23:163–198. doi: 10.1146/annurev.ge.23.120189.001115. [DOI] [PubMed] [Google Scholar]
  9. Gottesman S., Gottesman M., Shaw J. E., Pearson M. L. Protein degradation in E. coli: the lon mutation and bacteriophage lambda N and cII protein stability. Cell. 1981 Apr;24(1):225–233. doi: 10.1016/0092-8674(81)90518-3. [DOI] [PubMed] [Google Scholar]
  10. Kiino D. R., Phillips G. J., Silhavy T. J. Increased expression of the bifunctional protein PrlF suppresses overproduction lethality associated with exported beta-galactosidase hybrid proteins in Escherichia coli. J Bacteriol. 1990 Jan;172(1):185–192. doi: 10.1128/jb.172.1.185-192.1990. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Kiino D. R., Silhavy T. J. Mutation prlF1 relieves the lethality associated with export of beta-galactosidase hybrid proteins in Escherichia coli. J Bacteriol. 1984 Jun;158(3):878–883. doi: 10.1128/jb.158.3.878-883.1984. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Kumamoto C. A. SecB protein: a cytosolic export factor that associates with nascent exported proteins. J Bioenerg Biomembr. 1990 Jun;22(3):337–351. doi: 10.1007/BF00763171. [DOI] [PubMed] [Google Scholar]
  13. Lee C., Li P., Inouye H., Brickman E. R., Beckwith J. Genetic studies on the inability of beta-galactosidase to be translocated across the Escherichia coli cytoplasmic membrane. J Bacteriol. 1989 Sep;171(9):4609–4616. doi: 10.1128/jb.171.9.4609-4616.1989. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Lipinska B., Fayet O., Baird L., Georgopoulos C. Identification, characterization, and mapping of the Escherichia coli htrA gene, whose product is essential for bacterial growth only at elevated temperatures. J Bacteriol. 1989 Mar;171(3):1574–1584. doi: 10.1128/jb.171.3.1574-1584.1989. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Lipinska B., Zylicz M., Georgopoulos C. The HtrA (DegP) protein, essential for Escherichia coli survival at high temperatures, is an endopeptidase. J Bacteriol. 1990 Apr;172(4):1791–1797. doi: 10.1128/jb.172.4.1791-1797.1990. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Menon A. S., Goldberg A. L. Binding of nucleotides to the ATP-dependent protease La from Escherichia coli. J Biol Chem. 1987 Nov 5;262(31):14921–14928. [PubMed] [Google Scholar]
  17. Menon A. S., Goldberg A. L. Protein substrates activate the ATP-dependent protease La by promoting nucleotide binding and release of bound ADP. J Biol Chem. 1987 Nov 5;262(31):14929–14934. [PubMed] [Google Scholar]
  18. Phillips G. J., Silhavy T. J. Heat-shock proteins DnaK and GroEL facilitate export of LacZ hybrid proteins in E. coli. Nature. 1990 Apr 26;344(6269):882–884. doi: 10.1038/344882a0. [DOI] [PubMed] [Google Scholar]
  19. Phillips T. A., VanBogelen R. A., Neidhardt F. C. lon gene product of Escherichia coli is a heat-shock protein. J Bacteriol. 1984 Jul;159(1):283–287. doi: 10.1128/jb.159.1.283-287.1984. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Randall L. L., Hardy S. J. Correlation of competence for export with lack of tertiary structure of the mature species: a study in vivo of maltose-binding protein in E. coli. Cell. 1986 Sep 12;46(6):921–928. doi: 10.1016/0092-8674(86)90074-7. [DOI] [PubMed] [Google Scholar]
  21. Silhavy T. J., Benson S. A., Emr S. D. Mechanisms of protein localization. Microbiol Rev. 1983 Sep;47(3):313–344. doi: 10.1128/mr.47.3.313-344.1983. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Silhavy T. J., Shuman H. A., Beckwith J., Schwartz M. Use of gene fusions to study outer membrane protein localization in Escherichia coli. Proc Natl Acad Sci U S A. 1977 Dec;74(12):5411–5415. doi: 10.1073/pnas.74.12.5411. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Singer M., Baker T. A., Schnitzler G., Deischel S. M., Goel M., Dove W., Jaacks K. J., Grossman A. D., Erickson J. W., Gross C. A. A collection of strains containing genetically linked alternating antibiotic resistance elements for genetic mapping of Escherichia coli. Microbiol Rev. 1989 Mar;53(1):1–24. doi: 10.1128/mr.53.1.1-24.1989. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Slauch J. M., Silhavy T. J. Genetic analysis of the switch that controls porin gene expression in Escherichia coli K-12. J Mol Biol. 1989 Nov 20;210(2):281–292. doi: 10.1016/0022-2836(89)90330-6. [DOI] [PubMed] [Google Scholar]
  25. Stout V., Torres-Cabassa A., Maurizi M. R., Gutnick D., Gottesman S. RcsA, an unstable positive regulator of capsular polysaccharide synthesis. J Bacteriol. 1991 Mar;173(5):1738–1747. doi: 10.1128/jb.173.5.1738-1747.1991. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Strauch K. L., Beckwith J. An Escherichia coli mutation preventing degradation of abnormal periplasmic proteins. Proc Natl Acad Sci U S A. 1988 Mar;85(5):1576–1580. doi: 10.1073/pnas.85.5.1576. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Strauch K. L., Johnson K., Beckwith J. Characterization of degP, a gene required for proteolysis in the cell envelope and essential for growth of Escherichia coli at high temperature. J Bacteriol. 1989 May;171(5):2689–2696. doi: 10.1128/jb.171.5.2689-2696.1989. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Torres-Cabassa A. S., Gottesman S. Capsule synthesis in Escherichia coli K-12 is regulated by proteolysis. J Bacteriol. 1987 Mar;169(3):981–989. doi: 10.1128/jb.169.3.981-989.1987. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from Journal of Bacteriology are provided here courtesy of American Society for Microbiology (ASM)

RESOURCES