PhD ceremony: mw. L. Westers, 14.45 uur, Academiegebouw, Broerstraat 5, Groningen
Thesis: The bacell factory and therapeutic proteins
Promotor(s): prof. W.J. Quax
Faculty: Mathematics and Natural Sciences
The research of Lidia Westers was focussed on optimisation of the bacterium Bacillus subtilis for production of large amounts of proteins. The goal is to use this non-pathogenic bacterium for production of pharmaceutical proteins, e.g. human interleukin-3 (hIL-3), which can be used together with other medication in chemotherapy.
For production of hIL-3 different B. subtilis strains are uses in which protease genes are inactivated. Also, promoters on the overexpression plasmid are optimised and several signal peptides are used for optimal secretion of hIL-3 into the culture medium. By varying the culture media an optimal production system is achieved for hIL-3.
To make a variant with changed binding properties towards the hIL-3 receptor, 19 variants of hIL-3 are made at position Glu22. Most variants showed strongly decreased bioactivity towards leukemia cells. Binding experiments using Biacore showed that most of these less active variants still showed binding towards the hIL-3 specific
-subunit of the receptor. Of one of these less active variants it is shown that no hIL-3/hIL-3R complex is formed anymore.
The production and secretion of large quantities “foreign” proteins lead in B. subtilis to a stress response, lowering the final yield of the wanted protein. This so-called secretion stress response is studied further. It was shown that the intensity of this response can in some cases be used as an indicator for the protein production level.
Finally, an attempt was made to optimise the hIL-3 production system for the production of human TRAIL.
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