Identifying trigger factor functions and substrates
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In all kingdoms of life, proteins synthesis is carried out by the ribosome. Nascent chains leave the ribosome through a narrow tunnel in the large subunit, 50S. In bacteria, the first protein to interact with newly synthesized polypeptides is a ribosome-associated chaperone, trigger factor. The function of trigger factor on the ribosome has been well studied, but little is know the role of unbound trigger factor. Research in this thesis focuses on two proteins, trigger factor and tryptophanase, and their relationship. Tryptophanase was identified as a specific substrate of trigger factor using the two dimensional electrophoresis. Part of tryptophanase was found missing in tig-deletion E. coli strain. In vitro refolding experiment indicated that the recovered activity of tryptophanase can be improved 3 times with trigger factor. This indicates the potential function of trigger factor to facilitate the assembly of tryptophanase tetramer.