Detection of membrane-bound proteases of Francisella tularensis

Abstract

Sterile preparations of membrane fractions were prepared by processing of live Francisella tularensis cells of different subspecies with 4.5 M urea solution and differential centrifugation. For the first time, proteolytic activity was detected and studied by tests of radial enzyme diffusion and substrate polyacrylamide gel electrophoresis using gelatin as a substrate. Spectrum of gelatinases in the resulted preparation were detected. Quantitative inter-strain differences in the protease activities and their qualitative composition in membrane preparations of various virulent F. tularensis strains was analyzed. Avirulent F. tularensis 21/400 subsp. holarctica (1-214) strain demonstrated the greatest gelatinase activity in enzyme diffusion method and the lowest hydrolytic activity was seen in F. tularensis B-399 A-Cole subsp. tularensis (1-386) and F. tularensis Utah 112 subsp. novicida (1-384), other preparations showed intermediate activity. Enzyme electrophoresis in the protease spectra determined the presence of proteins with proteases activity 50-100 kDa, and in the spectrum preparations of F. tularensis 1-386 and 1-384 were detected additional bands of proteases.

Keywords

• francisella tularensis
• francisella tularensis
• subcellular fractions
• outer membrane
• enzyme
• protease
• proteolytic activity