Assembly Model of the Outer Membrane

On the basis of the data available at present, a tentative model of the E. coli outer membrane (illustrated diagramatically in Fig. 16) is postulated. This model has the following features [all numbers are calculated assuming that the cell s surface area is 4 (= 4 x 10 A )]  

The location of protein 6 (Y protein see Section 2.3) is not yet established. However, it is probably somewhat buried inside the outer membrane, since it is resistant to trypsin although not to pronase treatments. 

Protein 7 tol G protein see Section 2.4) is exposed to the outer surface of the outer membrane, making it sensitive to protease treatment(s). A part of protein 7 is buried within the outer membrane, so that after protease treatment, this part of the molecule is still left in the outer membrane as a smaller-molecular-weight fragment (see Inouye and Yee and also band II to band II in Henning et al. ). The part exposed to the outside of the cell provides the receptor for colicins. 

Protein 11 (channel lipoprotein see Section 2.5) forms channels through the outer membrane, providing passive diffusion pores. There are 

3 X 10 channels per cell, which occupy 35% of the total outer membrane structure. 

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