title: Extracellular secretion of a recombinant therapeutic peptide by Bacillus halodurans utilizing a modified flagellin type III secretion system.
abstract: BACKGROUND
  Through modification of the flagellin type III secretion pathway of Bacillus halodurans heterologous peptides could be secreted into the medium as flagellin fusion monomers. The stability of the secreted monomers was significantly enhanced through gene-targeted inactivation of host cell extracellular proteases. In evaluating the biotechnological potential of this extracellular secretion system an anti-viral therapeutic peptide, Enfuvirtide, was chosen. Currently, Enfuvirtide is synthesised utilizing 106 chemical steps. We used Enfuvirtide as a model system in an effort to develop a more cost-effective biological process for therapeutic peptide production.
  
  
  RESULTS
  An attempt was made to increase the levels of the fusion peptide by two strategies, namely strain improvement through gene-targeted knock-outs, as well as vector and cassette optimization. Both approaches proved to be successful. Through chromosomal inactivation of the spo0A, lytC and lytE genes, giving rise to strain B. halodurans BhFDL05S, the secretion of recombinant peptide fusions was increased 10-fold. Cassette optimization, incorporating an expression vector pNW33N and the N- and C-terminal regions of the flagellin monomer as an in-frame peptide fusion, resulted in a further 3.5-fold increase in the secretion of recombinant peptide fusions.
  
  
  CONCLUSIONS
  The type III flagellar secretion system of B. halodurans has been shown to successfully secrete a therapeutic peptide as a heterologous flagellin fusion. Improvements to both the strain and expression cassette led to increased levels of recombinant peptide, showing promise for a biotechnological application.
authors.affiliation: CSIR Biosciences, Box 395, Pretoria 0001, South Africa.
authors.forename: Eldie
authors.initials: E
authors.lastname: Berger
authors.forename: Michael C
authors.initials: MC
authors.lastname: Crampton
authors.forename: Nolwandle P
authors.initials: NP
authors.lastname: Nxumalo
authors.forename: Maureen E
authors.initials: ME
authors.lastname: Louw
mesh_terms: D001407:Bacillus / Q000378:metabolism*; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D000077560:Enfuvirtide; D005408:Flagellin / Q000235:genetics / Q000378:metabolism*; D055786:Gene Knockout Techniques; D015700:HIV Envelope Protein gp41 / Q000096:biosynthesis / Q000235:genetics; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D010446:Peptide Fragments / Q000096:biosynthesis / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D015700:HIV Envelope Protein gp41; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; C080950:Spo0A protein, Bacillus subtilis; D014157:Transcription Factors; D005408:Flagellin; D000077560:Enfuvirtide; C112181:LytE protein, Bacillus subtilis; D009238:N-Acetylmuramoyl-L-alanine Amidase