Electrophoretic resolution of the ‘major outer membrane protein’ of Escherichia coli K12 into four bands

The cell envelope of Enterobacteriaceae consists of two membranes separated by a peptidoglycan layer. Methods have been developed to separate the cytoplasmic membrane from the outer membrane. The outer membrane of Escherichia coli contains 60% of the envelope protein. Using polyacrylamide gelelectrophoresis, Schnaitman found six protein bands in the outer membrane fraction, of which one band (mol. wt 44 000) accounted for 70% of the total outer membrane protein