Structural and functional differences of the anionic and cationic antigens in K99 extracts of Escherichia coli B41

Radiolabelled anionic and cationic components were purified from K99 extracts of Escherichia coli B41 by immunoelectrophoresis using absorbed K99 antisera. SDS-polyacrylamide gel electrophoresis revealed that the apparent molecular weights of the polypeptide subunits were 34,000 and 19,000, respectively. Both anionic and cationic antigens in cell-free K99 extracts adhered to sheep erythrocytes after 90 min at 4 degrees C, but the cationic antigen eluted after a further 1 h at 37 degrees C. The anionic antigen did not elute from sheep erythrocytes after 18 h at 37, 43 or 56 degrees C.