Salt-Dependent Conditional Protein Splicing of an Intein from Halobacterium salinarum

An intein from Halobacterium salinarum can be isolated as an unspliced precursor protein with exogenous exteins after Escherichia coli overexpression. The intein promotes protein splicing and uncoupled N-terminal cleavage in vitro, conditional on incubation with NaCl or KCl at concentrations of >1.5 M. The protein splicing reaction also is conditional on reduction of a disulfide bond between two active site cysteines. Conditional protein splicing under these relatively mild conditions may lead to advances in intein-based biotechnology applications and hints at the possibility that this H. salinarum intein could serve as a switch to control extein activity under physiologically relevant conditions.