Exploitation of protein targeting pathways for biopharmaceutical production in E. coli

Background. The market for recombinant biopharmaceuticals such as antibody fragments, growth factors, hormones and other biologically-based medicines is estimated to be over $160 billion p.a. [1], with antibody products accounting for a large proportion of these sales [1-2]. Over a third of currently-licensed proteins are produced in Escherichia. coli, where ’export’ out of the cytoplasm to the periplasm is a favoured strategy. This minimises downstream processing (DSP) costs because (i) the target protein can be purified from the relatively simple periplasmic contents, and (ii) this strategy avoids debris and DNA contamination which are serious DSP problems.
There is a clear need for simpler, more cost-effective platforms to cope with current demand, and more capable E. coli-based systems would provide the ideal solution. This project aims to use synthetic biology approaches to develop new platforms that are based on the Tat protein export pathway in E. coli.

Aims of the project. The student will be involved in the following research:

1. Investigation of the Tat ’substrate proofreading’ activity. As well as being able to transport folded proteins, the Tat system has a natural tendency to transport only correctly folded proteins. This is a remarkable trait and this project will investigate the molecular basis for this ability. We have developed Tat mutants that show an altered substrate proofreading mechanism and the aim will be to determine how these Tat systems have been changed, and what they see as ’folded’.
2. Development of super-secreting E. coli strains. We have recently developed E. coli strains that overexpress Tat system components, and these strains exhibit significantly higher rates of Tat-dependent protein export. One of the project aims will be to test these strains’ abilities to secrete a range of ultra high value target proteins, particularly more complex proteins that cannot be exported by the traditional Sec pathway.

Training aspects of the project. The project will provide advanced training in the techniques involved in biopharmaceutical production, including design, expression and characterisation of target molecules, together with engineering of E. coli host strains.

Start Date: September 2017

To apply: To apply for this project please submit an on-line application for the PhD Cell Biology. Please enter the project title as the proposed research topic and enter Prof Colin Robinson as the supervisor. For the research proposal please enter "as advertised". Please include a cv and a covering letter.
Informal enquiries may be sent to Prof Colin Robinson: [Email Address Removed].
Closing date for applications: 31 March 2017