Localization and immunological characterization of the cellulolytic enzyme system inClostridium thermocellum

The cellulolytic enzyme complex from Clostridium thermocellum JW 20 was purified from the cellulose to which the enzyme was bound during growth. After centrifugation and gel filtration the enzyme complex was analyzed by SDS-PAGE. Three subunits with apparent molecular weights of 195 000 Da, 97 000 Da and 72 000 Da were purified by preparative SDS-PAGE and electroelution. Polyclonal antibodies directed against these three subunits were raised in rabbits. The specificity of the antisera was tested with immunochemical methods. Cross reactions with other subunits of the cellulase complex were observed. Immunoelectron microscopy of protein-A gold labeled, resin embedded cells indicated that the three types of subunits were located in the outer region of the cytoplasm and on structures at the outside of the cell wall.