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Melibiose Operon Expression System

Inactive Publication Date: 2008-12-11
LONZA AG
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0005]These and other objects as will be apparent from the foregoing description have been achieved by providing new vectors comprising a prokaryotic promoter region which is useful for high-level expression of a desired heterologous product. Surprisingly, it has been found that the promoter region of the melibiose operon allows for tightly regulated expression of high amounts of heterologous product. In a first aspect, the object of the present invention is to provide a new vector expressible in a host comprising the promoter region of the melibiose operon operably linked to a transcriptional unit comprising a nucleic acid sequence which is heterologous to said host, whereas the expression of said nucleic acid sequen

Problems solved by technology

However, most heterologous gene expression systems in prokaryotic host systems have relied exclusively on a limited set of bacterial promoters.
However, many of the known prokaryotic promoters used for heterologous gene expression have drawbacks such as the toxicity of the heterologous product to the host cell, low rates of expression of the product or the formation of non-functional aggregates (inclusion bodies).
Most of these inducible promoter systems used for homologous expression have the drawback that only low induction rates and therefore low expression of the desired homologous product have been achieved.
Furthermore, these promoter systems are not very tightly regulated thus leading to background activity in an uninduced state, which does not allow for strict expression control.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0077]The Escherichia coli W3110 genome was scanned for positively regulated operons. Based on the genomic data which are available on the KEGG database (Kyoto Encyclopedia of Genes and Genomes, http: / / www.genome.ad.jp / kegg / kegg2.html) positively regulated catabolic promoters were identified and analysed for their use in expression plasmids. The promoters should be tightly regulated and induced by a cheap and non-toxic and therefore industrially useful compound. The following promoters of different positively regulated catabolic operons were, chosen

Construction of Expression Plasmids with Positively Regulated Promoters[0078]prp promoter (propionate inducible)[0079]gutA promoter (glucitol inducible)[0080]melAB2 promoter (melibiose inducible)

The precise DNA fragments which contain the promoter elements were selected based on the available information on the corresponding regulator binding sites. Chromosomal DNA of Escherichia coli was isolated by the method of Pitcher et al., 1989, Le...

example 2

Construction of Fab Fragment Expression Plasmids

[0082]As an alternative to an IPTG-inducible lac promoter (plasmid pMx9-HuCAL-Fab-H, Knappik et al., 1985, Gene 33, 103-119), different positively regulated expression systems were analysed for their capacity to produce Fab-H antibody fragments. The Fab-H fragment was amplified out of plasmid pMx9-HuCAL-Fab-H by PCR using the primers Fab-5 (5′-aaa cat atg aaa aag aca gct atc-3′) and Fab-3 (5′-aaa aag ctt tta tca gct ttt cgg ttc-3′). The PCR-fragment was cut with NdeI and HindIII and inserted into NdeI / HindIII-cut pBW22 to create plasmid pBW22-Fab-H containing the L-rhamnose inducible rhaBAD promoter (Volff et al., 1996, Mol. Microbiol. 21, 1037-1047). The same PCR-fragment was inserted into the different expression plasmids with inducible promoters. The resulting (putative) expression plasmid pBLL15 containing Fab-H and the melAB2 promoter (SEQ ID NO. 3) is shown in FIG. 2. Equivalent plasmids containing the prp promoter (pBLL13) and t...

example 3

Expression of Fab Fragment

[0083]Strain W3110 (DSM 5911, Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, Braunschweig, Germany) was transformed with the different expression plasmids. The plasmids were isolated from clones which resulted from the different transformations and checked via restriction analysis. Except plasmid pBLL14 all plasmids had the expected restriction pattern. The re-isolated plasmid pBLL14 showed an altered size and restriction pattern which was suggested to be due to recombination events. Therefore strain W3110 (pBLL14) was not tested in the following assays. The remaining strains were tested for their ability to secrete actively folded Fab-H antibody fragments. This productivity test was performed as described in example 4. The following inducers were added in a concentration of 0.2%

pBW22-Fab-HL(+)-Rhamnose monohydratepBLL13Sodium propionatepBLL15D(+)-Melibiose monohydrateD(+)-Raffinose monohydrateD(+)-Galactose

[0084]The results from the dot blot ...

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Abstract

New vectors expressible in a host comprising the promoter region of the melibiose operon operably linked to a transcriptional unit that includes nucleic acid sequence which is heterologous to the host. The expression of the nucleic acid sequence is controlled by the promoter region of the melibiose operon. The new vector can be used for the regulated heterologous expression of a nucleic acid sequence in a prokaryotic host. There is an isolated and purified nucleic acid sequence expressible in a host comprising the promoter region of the melibiose operon operably linked to a transcriptional unit that includes a nucleic acid sequence which is heterologous to the host. The expression of the nucleic acid sequence is controlled by the promoter region of the melibiose operon. A prokaryotic host is transformed with the vector or the isolated and purified nucleic acid sequence. There is a method for producing a polypeptide in a host using the vector.

Description

[0001]The present invention concerns vectors for the heterologous expression of nucleic acids encoding e.g. polypeptides such as recombinant proteins in prokaryotic hosts. More specifically, the present invention relates to new vectors expressible in a host comprising the promoter region of the melibiose operon operably linked to a transcriptional unit comprising a nucleic acid sequence which is heterologous to said host, whereas the expression of said nucleic acid sequence is controlled by said promoter region of the melibiose operon. The present invention relates further to the use of these vectors for the heterologous expression of nucleic acids encoding e.g. polypeptides.BACKGROUND OF THE INVENTION[0002]Many systems have been described for the heterologous expression of nucleic acids encoding e.g. polypeptides such as recombinant proteins in prokaryotic systems. However, most heterologous gene expression systems in prokaryotic host systems have relied exclusively on a limited se...

Claims

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Application Information

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IPC IPC(8): C12P21/04C12N15/00C12N15/11C12N1/20
CPCC07K14/70C07K16/00C12N15/52C07K2317/622C07K2319/00C07K2317/55
Inventor BRASS, JOHANNKLEIN, JOACHIMOSTENDORP, RALF
Owner LONZA AG
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