Proteins of the Outer Membrane of Gram-Negative Bacteria

Characterization of the motion of membrane proteins using high-speed atomic force microscopy

“…Early electron microscopy studies have indicated a high density of porin packing in the outer membrane, which is likely to result in significantly restricted protein movement 5,23 . In the crowded membrane, HS-AFM provides evidence that the displacement of one molecule can induce a chain motion, allowing movement of another molecule ( Supplementary Fig.…”

Synthesis of OmpA Protein of Escherichia coli K12 in Bacillus subtilis

“…The mechanism of this transfer is unknown (for a review, see Lugtenberg & van Alphen, 1983;Pugsley & Schwartz, 1985). Some hypothetical models (Henning et al, 1983;Osborn & Wu, 1980) suggest that OM proteins may travel across the periplasmic space in soluble form not bound to membrane structures. Such a form would seemingly be analogous to periplasmic proteins and expected to be secreted -like the /3-lactamase -also across the cytoplasmic membrane of B. subtilis when fused to the signal peptide of a-amylase.…”

“…Their purification is, however, tedious and seldom achievable under mild conditions (for a review, see Lugtenberg & van Alphen, 1983) largely due to their amphipathic or hydrophobic character, which leads to aggregation with other proteins and glycolipids of the cell envelope (Hofstra & Dankert, 1980;Kuusi et al, 1981 ;Lugtenberg & van Alphen, 1983). Furthermore, at least two classes of major OM proteins -the pore forming porins and the OmpA protein -have a specific affinity to lipopolysaccharide (van Alphen et al, 1979;Lugtenberg & van Alphen, 1983;Osborn & Wu, 1980;Schindler & Rosenbusch, 1981;Schweizer et al, 1978;Yamada & Mizushima, 1980), so that these proteins cannot be separated from lipopolysaccharide without extensive denaturation (Furukawa et al, 1979;Overbeeke et al, 1980;see also Lugtenberg & van Alphen, 1983;Vaara & Nikaido, 1984).…”

Molecular cloning and expression in E. coli of a Salmonella typhi porin gene

“…Porins are bacterial outer membrane proteins capable of forming pores that are involved in the permeability of low molecular mass substances of hydrophilic nature [1,2]. Porins from E. coli and Salmonella typhimurium have been extensively studied [3,4].…”