Architecture of the outer membrane of Escherichia coli K12 IV. Relationship between outer membrane particles and aqueous pores

Abstract

SummaryThe hypothesis that intramembraneous particles, observed in the outer membrane of Escherichia coli by freeze-fracture electron microscopy, are the morphological representation of aqueous pores, was tested. A mutant which is deficient in five major outer membrane proteins, b, c, d, e and the phage receptor protein, contains a largely decreased number of intramembraneous particles and also shows a greatly decreased rate of uptake of several solutes. In derivatives of this strain which contain only one of these proteins in large amounts a strong decrease of the number of intramembraneous particles is observed, which is accompanied by a complete restoration of the rate of uptake of those solutes which use pores in which the protein in question is involved. The results provide strong evidence for the notion that an individual pore contains only one protein species, a property which has been found earlier for individual particles. The observed correlation between particles and aqueous pores strongly supports the hypothesis that the particles are the morphological representation of pores. Implications of this hypothesis for the structure of the particles are discussed.

31P nuclear magnetic resonance and freeze-fracture electron microscopy studies on Escherichia coli. III. The outer membrane

“…It has been suggested that these particles contain hemi-micelles of lipopolysaccharide [10--12,14]. If this is the case the NMR results indicate that there is probably little diffusional motion of the lipopolysaccharide around the curved surfaces of the particles and that it is likely that the major outer membrane proteins b, c and d, which are also thought to be present in the particles and which are probably complexed with lipopolysaccharide [14], can immobilize lipopolysaccharide in the particles.…”

“…In mutant cells which lack most of the major outer membrane proteins there is a large reduction in the number of particles and pits [11--13]. It has been suggested that these particles contain hemi-micellar lipopolysaccharide structures which form the basis of pores through the outer membrane [ 14].…”

TheTreponema denticolaMajor Sheath Protein Is Predominantly Periplasmic and Has Only Limited Surface Exposure

“…Proteinaceous two-dimensional arrays typically are extrinsic to bacterial outer membranes (hence their designation as surface-or S-layers) rather than embedded within them (46). Porin trimers, on the other hand, are tightly packed within gram-negative bacterial outer membranes (50,56) but do not normally form true polygonal arrays (34,49). Lastly, the recent demonstration by Fenno et.…”

The influence of food preservation methods on Escherichia coli, Salmonella enteritidis and Pseudomonas aeruginosa lipopolysaccharide composition and liberation

“…The toxicity of lipid A moieties depend on the number and the nature of fatty acids (Caroff et al, 2002). Numerous researchers have reported on changes in the Lipid A structure and configuration in different Gram-negative bacteria including E. coli and Salmonella tyhimurium (Van Alphen et al, 1979;Guo et al, 1997) and the effect thereof on the toxicity of the subsequent molecule. Considering the data presented in this study, it is evident that changes occurred in the lipid A moiety of all the organisms investigated.…”