Studies on bacterial chemotaxis. I. Separation of proteins from cell envelope of Escherichia coli

Radioactive proteins from Escherichia coli cell envelope fraction were separated by two-dimensional polyacrylamide gel electrophoresis. Electrophoresis was carried out under several sets of conditions, and autoradiographs were obtained. Many of the proteins were separated at well-defined positions with good reproducibility. Some of the proteins moved relative to these stationary proteins depending at least two factors, i.e. the amount of proteins applied in the first dimension and the electric current applied in the second dimension. Among more than 200 spots, methyl-accepting chemotaxis protein and flagellin were identified by using labelled or cold preparations of these proteins as markers. Some of the spots were assigned to proteins from the outer membrane of the bacteria. The results provide a good foundation for comparative studies of membrane proteins from genetically altered strains of the bacteria.