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Gene Review

sopB  -  plasmid-partitioning protein

Escherichia coli O157:H7 str. Sakai

 
 
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Disease relevance of sopB

  • Expression of a high level of F-plasmid-encoded SopB protein in Escherichia coli is found to repress genes linked to sopC, a sequence element of F consisting of 12 tandemly joined imperfect repeats of a 43-bp motif [1].
  • We have recently characterized SopB, a novel secreted effector protein of Salmonella dublin, and presented evidence that SopB is translocated into eukaryotic cells via a sip-dependent pathway to promote fluid secretion and inflammatory responses [2].
 

High impact information on sopB

  • We show that SopA is a dynamic protein within the cell, undergoing cycles of polymerization and depolymerization, and shuttling back and forth between nucleoprotein complexes that are composed of the SopB protein bound to sopC-containing plasmids (SopB/sopC) [3].
  • The subcellular localization of the SopB protein, which is encoded by the Escherichia coli F plasmid and is involved in the partition of the single-copy plasmid, was directly visualized through the expression of the protein fused to the jellyfish green fluorescent protein (GFP) [4].
  • Our experiments suggest that SopB bound at a single site nucleates the binding of additional SopB protein and wrapping of adjacent DNA sequences, such that approximately equal numbers of supercoils are restrained regardless of the number of tandem sopC repeats present [5].
  • In this study, we demonstrate that a functional partition complex can form with a single 43-bp SopB binding site [5].
  • An excess of SopB protein does not extend its in vitro binding outside sopC, implicating participation of a host factor(s) in SopB-mediated gene silencing [6].
 

Biological context of sopB

  • It is plausible that the near polar localization of SopB may serve the function of keeping a segregated pair of F plasmids apart while the cell septum is being formed [4].
  • We have found that SopB protein acting at sopC in vivo is associated with a marked effect on plasmid DNA supercoiling, which may reflect the formation of a wrapped nucleoprotein complex [5].
  • On the other hand, SopB protein binds to the sopC region, in which 12 direct repeats of 43-base pairs nucleotides exist [7].
  • SopB protein recognizes the inverted repeats of 7 base pairs in each direct repeats [7].
  • The resulting SopB deficit is proposed to delay partition complex formation and facilitate pairing between mini-F and the centromere vector, thereby increasing randomization of segregation [8].
 

Anatomical context of sopB

  • Alternative strategies have been developed by Salmonella to induce intestinal secretion through the elaboration of a factor (SopB) that resembles at least two of the host cell 4-phosphatases, enzymes that activate the Ca-dependent transcellular secretion pathway [9].
 

Analytical, diagnostic and therapeutic context of sopB

References

  1. SopB protein-mediated silencing of genes linked to the sopC locus of Escherichia coli F plasmid. Lynch, A.S., Wang, J.C. Proc. Natl. Acad. Sci. U.S.A. (1995) [Pubmed]
  2. Identification of a pathogenicity island required for Salmonella enteropathogenicity. Wood, M.W., Jones, M.A., Watson, P.R., Hedges, S., Wallis, T.S., Galyov, E.E. Mol. Microbiol. (1998) [Pubmed]
  3. Bacterial DNA segregation by dynamic SopA polymers. Lim, G.E., Derman, A.I., Pogliano, J. Proc. Natl. Acad. Sci. U.S.A. (2005) [Pubmed]
  4. Localization of F plasmid SopB protein to positions near the poles of Escherichia coli cells. Kim, S.K., Wang, J.C. Proc. Natl. Acad. Sci. U.S.A. (1998) [Pubmed]
  5. A single 43-bp sopC repeat of plasmid mini-F is sufficient to allow assembly of a functional nucleoprotein partition complex. Biek, D.P., Shi, J. Proc. Natl. Acad. Sci. U.S.A. (1994) [Pubmed]
  6. Molecular dissection of a protein SopB essential for Escherichia coli F plasmid partition. Hanai, R., Liu, R., Benedetti, P., Caron, P.R., Lynch, A.S., Wang, J.C. J. Biol. Chem. (1996) [Pubmed]
  7. Purification and characterization of SopA and SopB proteins essential for F plasmid partitioning. Mori, H., Mori, Y., Ichinose, C., Niki, H., Ogura, T., Kato, A., Hiraga, S. J. Biol. Chem. (1989) [Pubmed]
  8. Probing plasmid partition with centromere-based incompatibility. Bouet, J.Y., Rech, J., Egloff, S., Biek, D.P., Lane, D. Mol. Microbiol. (2005) [Pubmed]
  9. Cross-talk between enteric pathogens and the intestine. Uzzau, S., Fasano, A. Cell. Microbiol. (2000) [Pubmed]
  10. Autoregulation of the partition genes of the mini-F plasmid and the intracellular localization of their products in Escherichia coli. Hirano, M., Mori, H., Onogi, T., Yamazoe, M., Niki, H., Ogura, T., Hiraga, S. Mol. Gen. Genet. (1998) [Pubmed]
 
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