Expression and subcellular location of native and mutant hTNFα proteins in Escheriahia coli

Abstract Several mutant hTNFα genes were constructed by deletion and stepwise reconstitution of regions coding for C-terminal sequences. The mutant hTNFα proteins behaved differently from native hTNFα when expressed in Escherichia coli . They were either sensitive to proteolytic degradation or formed insoluble aggregates depending on the strains and conditions used for expression. By contrast, native hTNFα was always present in a soluble form and had a tendency to associate with the cytoplasmic membrane. It was even transported to the periplasmic space in E. coli as shown by both cell fractionation and immunoelectron microscopy. The different behaviour of mutant hTNFα proteins probably results from a disturbance of protein folding.