IGEM:IMPERIAL/2007/Projects/In-Veso
In-Veso Gene Expression: Introduction
The vesicle chassis is an addition to the Registry of Standard Biological Parts. In these pages we detail the techniques and characteristics of its use.
The specification, design, modelling, implementation, and testing cycle is applied to the characterisation of the chassis. The specifications outline the characteristics of the chassis being sought, and the quantities that will be varied in experiments. The design elaborates how these characteristics will be obtained, including experimental protocols, and experiment schedules. Some characteristics are obtained from literature, and these are not covered in the design. In modelling, we seek to refine the experimental design, identify expected points of interest in the results, and provide a more abstracted description of the chassis itself. The section on implementation covers the actual experiments and their results. Finally, in testing and validation, the results are analysed and compared to the modelling and specifications.
The E.coli In Vitro Gene Expression System
The in vitro expression of proteins in cell-free extracts is an important tool for molecular biologists and has a variety of applications. The use of in vitro translation systems can have advantages over in vivo gene expression when the over-expressed product is toxic to the host cell, when the product is insoluble or forms inclusion bodies, or when the protein undergoes rapid proteolytic degradation by intracellular proteases. [1] The big advantage of the in vitro approach in our projects, is that it enables the detection of biofilm on medical devices and the detection of spoilage in meat, without actually having to place E.coli in contact with the medical devices or the meat.
There are two approaches to in vitro protein synthesis based on the starting genetic material: RNA or DNA. Standard translation systems use RNA as a template; whereas coupled transcription-translation systems start with DNA templates, which are transcribed into RNA then translated. DNA templates for coupled transcription-translation systems can be easily generated by PCR. The most frequently used cell-free systems consist of extracts from rabbit reticulocytes, wheat germ and E.coli. For the purposes of our projects, the E.coli system looks more attractive than the eukaryotic systems.
Unlike eukaryotic systems where transcription and translation occur sequentially, in E. coli systems, coupled transcription and translation occur simultaneously in the same tube under the same reaction conditions. This bacterial system gives efficient expression of either prokaryotic or eukaryotic gene products in a short amount of time. Capping of eukaryotic RNA is not required. Use of E.coli extract also eliminates cross-reactivity or other problems associated with endogenous proteins in eukaryotic lysates. In addition, the E. coli S30 extract system allows expression from DNA vectors containing natural E. coli promoter sequences (such as lac).
The following are some papers that use the E.coli S30 extract for in vitro protein synthesis:
- Wetekam W, Staack K, and Ehring R. DNA-dependent in vitro synthesis of enzymes of the galactose operon of Escherichia coli. Mol Gen Genet. 1971;112(1):14-27. DOI:10.1007/BF00266928 |
- Zubay G. In vitro synthesis of protein in microbial systems. Annu Rev Genet. 1973;7:267-87. DOI:10.1146/annurev.ge.07.120173.001411 |
The In-Veso Technque
Write introduction to in-veso here. Dirk 17:03, 26 July 2007 (EDT)
