Location of Repository

Organisation and mechanism of bacterial twin arginine translocases

By James Paul Barnett

Abstract

The bacterial Tat pathway facilitates the translocation of pre-folded proteins over the cytoplasmic membrane. In Gram-negative bacteria, TatA, TatB and TatC (each an integral membrane protein) are the essential components. Most of our understanding of Tat function in bacteria has come from studies on Escherichia coli, a Gramnegative bacterium. \ud Gram-positive bacteria have Tat systems that are composed of just a single TatA and TatC protein. The absence of TatB suggests a different organisation and translocation mechanism to the Tat systems of Gram-negative bacteria. \ud Here the Tat pathway of Bacillus subtilis, a Gram-positive bacterium, was analysed in detail for the first time revealing important structural differences to the E. coli Tat pathway. \ud Complementation experiments reveal the Tat pathway of B. subtilis is active in E. coli, pointing to functional conservation between Gram-negative and Gram-positive bacteria. \ud The complexes formed by TatA and TatC in B. subtilis were investigated. TatA and TatC form a tight complex that is significantly smaller than its E. coli TatABC counterpart, possibly reflecting the presence of a different number of TatA and/or TatC units within this complex. TatA in B. subtilis like in E. coli also forms homooligomeric complexes separately from TatC. Unlike E. coli TatA complexes that vary enormously in size, the TatA complexes of Gram-positive bacteria are small and homogeneous in nature, suggesting an entirely different translocation mechanism involving a single defined translocon rather than a spectrum of size variants as proposed for E. coli. \ud The TatA proteins from Gram-positive bacteria may be bifunctional and perform the roles of E. coli TatA and TatB. Here the first direct evidence to support this hypothesis is presented and domains important for both TatA and TatB roles identified. \ud Finally a soluble population of TatA identified in B. subtilis was analysed and evidence is presented that suggests it maybe mis-localised

Topics: QR
OAI identifier: oai:wrap.warwick.ac.uk:2738

Suggested articles

Preview

Citations

  1. (2008). A facile reporter system for the experimental identification of twin-arginine translocation (Tat) signal peptides from all kingdoms of life. doi
  2. (1998). A novel and ubiquitous system for membrane targeting and secretion of cofactor-containing proteins. doi
  3. (2009). Contributions of the transmembrane domain and a key acidic motif to assembly and function of the TatA complex. doi
  4. (2007). Expression level of heterologous tat genes is crucial for in vivo reconstitution of a functional Tat translocase in Escherichia coli. doi
  5. (2001). Functional reconstitution of bacterial Tat translocation in vitro. doi
  6. (1986). Host/vector interactions which affect the viability of recombinant phage lambda clones. doi
  7. (1988). Purification and properties of Escherichia coli dimethyl sulfoxide, an iron-sulfur molybdoenzyme with broad substrate specificity.
  8. (2002). Sequence and phylogenetic analyses of the twin-arginine targeting (Tat) protein export system.
  9. (2000). TatD is a cytoplasmic protein with DNase activity. No requirement for TatD family proteins in sec-independent protein export. doi
  10. (2006). The TatAd component of the Bacillus subtilis twin-arginine protein transport system forms homo-multimeric complexes in its cytosolic and membrane embedded localisation. doi
  11. (2006). The twin-arginine translocation pathway is a major route of protein export in Streptomyces coelicolor. doi

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.