Functional expression, purification, and biochemical properties of subtilase SprP from Pseudomonas aeruginosa

The Pseudomonas aeruginosa genome encodes a variety of different proteolytic enzymes several of which play an important role as virulence factors. Interestingly, only two of these proteases are predicted to belong to the subtilase family and we have recently studied the physiological role of the subtilase SprP. Here, we describe the functional overexpression of SprP in Escherichia coli using a novel expression and secretion system. We show that SprP is autocatalytically activated by proteolysis and exhibits optimal activity at 50°C in a pH range of 7-8. We also demonstrate a significant increase in sprP promoter activity upon growth of P. aeruginosa at 43°C indicating a role for SprP in heat shock response.