Molecular weight determination and partial characterization of Klebsiella pneumoniae hemolysins.

Two thiol-activated Klebsiella pneumoniae hemolysins were purified from growth media by means of salt precipitation, gel filtration, ion-exchange chromatography, and polyacrylamide gel electrophoresis. The hemolysins peaks coincided with the protein and glycoprotein peaks as determined by chromatography and electrophoresis. The molecular weights, estimated by gel filtration, were 8400 and 19,000; by sodium dodecyl sulfate--polyacrylamide gel electrophoresis, the values were calculated as 15,500 and 27,000. The electrophoretic bands were best detected by the periodic acid--Schiff method. Reduction of the disulfide linkages did not cause the originally larger molecule to break into 8400 and 19,000 hemolysins. However, trypsin treatment cleaved the 19,000 hemolysin into an active moiety, with an electrophoretic migration similar to the 8400 hemolysin. A naturally occurring proteolytic activity was investigated using pepstatin and antipain. When the trypsin inhibitor was added to the system, the hemolytic activity was detected only in the 19,000 hemolysin and the smaller hemolysin was absent.