Influence of osmotic shock on Escherichia coli insoluble protein fraction in the presence of exogenous osmolytes

Abstract

The influence of osmotic shock in the presence of exogenous osmolytes on the formation and composition of insoluble protein fraction in Escherichia coli was investigated. Interferon-α5 (IFN-α5) expressed in E. coli BL21(DE3) was used as a model protein. Cells were cultivated at three different temperatures of 25, 30, and 37°C. Two different osmolytes were used. Glycine as an amino acid metabolized by E. coli, or betaine which is not metabolized by cells, was added to the growth medium in the presence of salt. In both cases (i.e. when metabolized or non-metabolized amino acid was used), IFN-α5 formed the aggregates, except at 25°C of cultivation. Moreover, the differences in the quantitative composition of insoluble protein fraction were revealed by the proteomic analysis. The amount of some identified proteins increased, decreased, or did not change in the samples cultivated under osmotic shock in the presence of betaine as compared with the sample cultivated without salt and betaine in growth medium.