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Analysis of periplasmic proteins induced in Escherichia coli strains genetically selected for enhanced protein folding
KTH, School of Biotechnology (BIO).
2014 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Proteins in the cellular environment must attain their functional folds even under the crowded cellular conditions which can favor side reactions that lead to aggregation. To prevent loss of protein function and formation of toxic aggregates, cells utilize diverse stress responses when unfavorable conditions arise. Molecular chaperones aid in protein folding and help prevent aggregation. As a consequence, many of these proteins are essential for survival under stressful conditions. The periplasm of gram-negative bacteria is especially sensitive to environmental changes, due to the high permeability of the outer membrane. Surprisingly, few chaperones are known in this compartment. In this study, two periplasmic proteins ArtI and OsmY were characterized, both of which had been identified by a genetic selection system for enhanced protein folding in Escherichia coli.

ArtI does not exhibit chaperone activity in vitro on model substrates or in vivo on an unstable protein. OsmY does inhibit protein aggregation and enhances the function of an unstable protein in vivo when overexpressed, providing evidence that OsmY is a novel molecular chaperone. OsmY was also analyzed with regards to its extracellular localization. OsmY exists in the culture medium to a higher level than another periplasmic control protein, and truncations of OsmY can be used to facilitate extracellular production of proteins fused to it. Future work will be needed to determine whether OsmY is secreted by E. coli using an active mechanism or escapes the cell in a more passive manner.

Place, publisher, year, edition, pages
Keyword [en]
Periplasm, E.coli, chaperones, selection, extracellular
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-163670OAI: diva2:801723
Available from: 2015-04-14 Created: 2015-04-10 Last updated: 2015-09-15Bibliographically approved

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