ISSN:
1572-9699
Keywords:
protein secretion
;
Bacillus brevis host-vector system
;
cell surface structure
;
signal peptide
;
protein folding enzyme
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Many strains ofBacillus brevis were isolated from nature as very efficient producers of extracellular proteins. Strains identified asB. brevis including these protein-hyperproducers were reclassified into at least 6 species according to numerical analysis, DNA base composition, and DNA-DNA hybridization. We developed a host-vector system using appropriate strains of theseBacillus brevis as a host, which is excellent for the secretion of heterologous proteins. Utilizing the powerful promoters and signal peptide-coding regions of the cell wall protein gene, various expression-secretion vectors were constructed. The cell wall protein genes of theseB. brevis are transcribed from multiple and tandemly arranged promoters. Transcription from P2, one of the major promoters among them, was enhanced at the early stationary phase of growth, when divalent cations in the medium was depleted and the cell wall protein layers started to be shed. Translation of the cell wall protein gene transcripts starts at the two sites located tandemly in the same reading frame. The two forms of secretory precursors, translation products from the two sites, are cleaved at the same position giving rise to the same mature proteins. The nucleotide sequence from the promoter to the translation start site is highly conserved in protein-hyperproducingB. brevis. For the efficient secretion of some heterologous proteins, protein-hypersecreting mutants had to be selected. The engineering of the signal peptide was also often necessary to obtain a good secretion of heterologous proteins. Thus, high levels of secretion were achieved only after extensive improvements were made for host, vector and culture conditions. From these experimental results, a great deal of diversity has been observed in various aspects of protein secretion.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00873023
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