The mode of action of colicin E2 with regard to the structure of the Escherichia coli cell envelope.

The importance of cell membranes in maintaining the structural integrity of living organisms has been known for some time. A very complex and important role for membranes as the spatial and temporal organizers of the cell's numerous metabolic functions is presently being unfurled. Although overall membrane structure may appear to be similar amongst the vast range of living organisms, the basic framework is necessarily adorned with specialized coordinated systems relevant to each cell's functions. The mechanism of colicin E2 interaction with the cell surface of Escherichia coli is examined and discussed. Colicin action upon the bacterial cell's biochemical processes is both indirect and highly specific, and is mediated by some transmission system in the bacterial cell membrane. Fluorescein labelled colicin E2 and ferritin labelled anti-E2 Y globulin have been prepared and used in an attempt to locate the positions of colicin E2 molecules in or on the cell surface of sensitive bacteria. Generalized disturbance of cell envelope integrity subsequent to colicin action has been sought but not found. The highly specific nature of colicin action upon the membrane is supported. Treatments designed to interfere uith bacterial cell envelope integrity perturb the action of colicin E2. Hembrane fractionation procedures suitable for studying bacterial membrane structure are presently becoming available. An additional membrane fractionation procedure is presented, based upon the interaction of cadmium N-lauroyl sarcosinate with bacterial cell extracts. Sodium dodecyl sulphate acrylamide gel electrophoretic separation of E. coli envelope proteins from mutants refractory to the action of colicin E2 has shoun that these membrane-containing structures have an altered protein component compared to the non-refractory parental strain. Hypotheses explaining a certain type of colicin E2 refractivity are presented. Future studies involving the use of colicins and genetic analysis as effective tools in probing the complexities of the E. coli cell membrane structure are outlined.