Cloning and Expression of Serratia marcescens Protease Gene in Escherichia coli

A 5.8 kb chromosomal DNA fragment of Serratia marcescens ATCC 27117 including an extracellular serine protease gene was cloned in Escherichia coli. The cloned gene(pSMP18) caused specific excretion of the protease into the extracellular medium through the outer membrane of E. coli host cells. The protease purified from E. coli harboring pSMP18 was inactivated not by 100 mM EDTA but by 10 mM phenyl methyl sulfonyl flouride (PMSF). The molecular weight of the purified serine protease was about 66, 000 in the SDS-PAGE and the isoelectric point was approximately 5.7 in IEFㆍGel electrophoresis. The optimal pH and temperature for reaction of the purified serine protease were 9.5 and $45^\circ{C}$, respectively.