Conversion of bacterial gene products to secretion-competent fusion proteins

We describe an efficient and easy procedure that allows the generation, detection and secretion of foreign proteins by the secretion apparatus of E. coli hemolysin. The gene (or gene fragment) encoding the foreign protein (or protein domain) is inserted in-frame into a residual portion of the hemolysin gene (hlyA), encoding the HlyA secretion signal (HlyAs). Generally, the expressed fusion is efficiently secreted into the culture supernatant of the producing strain. The new approach allows the direct generation of fusion proteins from genomic DNA fragments. The successful use of this method is demonstrated by cloning of random chromosomal DNA fragments from Salmonella typhimurium.