SspB cysteine protease of Staphylococcus aureus promotes detachment of human keratinocytes and degrades fibronectin and vitronectin

by Massimi, Isabella

SspB cysteine protease of Staphyl~~~~~us aureuc promotcs detachment of human keratinocytcs and degrades fibronectin and vitronectin babella Massimi, M.Sc., 2001 Deparmient of Laboratory Medicine and Pathobiology University of Toronto SspB cysteine protease of S. aureus is coded for by the sspB gene, the second open nading h e of the ssp operon in which it is preceded by the sspA gene (V8 protease) and followed by the sspC gene. The 40 kDa precursor form of SspB (p-SspB) was expressed alone and in tandem with the sspC gene. In the presence of SspC, p-SspB showed greater activity by gelatin zymography. This may indicated a chaperone function for SspC. Purified p-SspB was processed by V8 protease to the mature, 22 kDa m-SspB. Purified m-SspB was shown to promote keratinocyte detachment. Also, m-SspB was shown to cleave fibronectin and vitronectin but not BSA, IgG or fibrinogen. These results may demonstrate that SspB is expressed as a zymogen, that is converted to an active protease, m-SspB, and that m-SspB may have an important virulence hinction in S. aureus pathogenesis through proteolysis of host proteins. - -a