FIG. 8.

Protease activation in the extracellular protein fraction from P. gingivalis FLL93. P. gingivalis was grown to stationary phase (OD₆₀₀ of 1.3) in 1 liter of BHI broth supplemented with hemin and vitamin K. Acetone (37.5%)-precipitated proteins were mixed with 8 M urea and were incubated at 4°C for 1 h. The urea was slowly removed from the mixture by centrifugation (10,000 × g) in a Millipore filtration unit with the addition of increasing volumes of 100 mM Tris-HCl buffer (pH 7.4). Activities for Rgp and Kgp were tested. Error bars indicate the standard errors of the means of three independent trials.