Myxobacterial slime and proteolytic activity

An extracellular protein-polysaccharide-lipide (PPL) complex from exponentially growing cultures of Myxococcus virescens was purified by phosphate precipitation and gel chromatography. The high molecular weight slime polymer appeared homogenous upon isoelectric focusing. The PPL complex exhibited proteolytic activity against gelatin and the activity was only partly reduced by heat treatment. The function of the slime polymer as protein denatured was studied. The complex formed micelles similar to anionic detergents and it inhibited the precipitation and coagulation of proteins by trichloroacetic acid. Lysozyme was totally inactivated when treated with the PPL complex. By gel chromatography binding studies, the PPl complex was found to bind lysozyme in the ratio of 1 to 5.8 (w/w). After separation of added protein from the complex the anticoagulation effect on the protein remained. The biological function of the PPL complex was demonstrated with hemoglobin. When all susceptible peptide bonds in PPL-treated hemoglobin were hydrolyzed by trypsin only 20% in the urea-denatured protein were attacked. The combined role of slime and proteolytic activity is discussed.Abbreviations Used PPL protein-polysaccharide-lipide - TCA trichloroacetic acid - BSA bovine serum albumin - Tris tris-(hydroxymethyl)aminomethane - CMC critical micelle concentration - DNFB 2,4-dinitrofluorobenzene - DNP N-dinitrophenyl - SDS sodium dodecylsulphate - H.U. Hultin units