Expression vector promoting the synthesis and export of the human growth-hormone-releasing factor in Escherichia coli

Abstract We have studied the synthesis, processing and export of human growth-hormone-releasing factor (hGRF) in Escherichia coli transformed with a plasmid constructed for the expression of hGRF as a hybrid protein. A DNA fragment containing the entire sequence of phosphate-binding protein gene ( phoS ) is fused to a modified hGRF-coding sequence ( phoS-mhGRF ). The hybrid protein, PhoS-mhGRF, was recovered in the supernatant fluid after spheroplasting treatment indicating correct export to the periplasmic space. Pulse-chase experiments demonstrated that the hybrid protein was similarly processed as the PhoS precursor.