Identification of host factors limiting the overexpression of recombinant Cu, Zn superoxide dismutase in Escherichia coli.

Abstract

Superoxide dismutase (SOD) enzyme has implications in modulating the cell's redox state. The study aims to explore the host genetic factors that limit the heterologous expression of a thermostable SOD from Potentilla atrosanguinea (Pa-SOD) in E. coli. It was observed that the heterologous expression of Pa-SOD in E. coli did not exhibit any enhancement after 1h of induction. This led to the alteration in cell morphology and an increase in the doubling time of E. coli cells expressing Pa-SOD. Label-free quantification and MALDI-TOF/TOF-MS/MS analysis suggested differential expression of 81 proteins, of which 77 proteins were found to be downregulated and 4 were found to be upregulated in Pa-SOD expressing cells as compared to uninduced E. coli cells. Functional analysis of downregulated proteins shows involvement in molecular function, biological process, and were the part of a cellular component. The STRING database revealed interaction of an essential autoregulatory protein, RNase E with other proteins involved in biosynthetic processes, protein biosynthesis and folding, and cell division. Further, validation of RNase E protein revealed upregulation of rne at transcript level and downregulation of RNase E at protein level as compared to uninduced cells. The observations suggested the operation of multifaceted mechanisms with a key role of RNase E that regulated the expression of Pa-SOD at the physiological and molecular level. Since Pa-SOD has commercial applications, identification and manipulation of these networked genetic factors could lead to improvement of host strain for large-scale production of biologically active Pa-SOD and other heterologous proteins.