Major outer membrane proteins Gram-negative bacteria

Currently, five different molecular classes of mdr efflux pumps are known [5], While pumps of the the ATP-binding cassette (ABC) transporter superfamily are driven by ATP hydrolysis, the other four superfamilies called resistance-nodulation-division (RND), major facilitator superfamily (MFS), multidrug and toxic compound extrusion (MATE), and small multidrag resistance transporter (SMR) are driven by the proton-motive force across the cytoplasmic membrane. Usually a single pump protein is located within the cytoplasmic membrane. However, the RND-type pumps which are restricted to Gram-negative bacteria consist of two additional components, a periplasmic membrane fusion protein (MFP) which connects the efflux pump to an outer... 

Chloramphenicol inhibits protein synthesis by binding the 50S ribosomal subunit and preventing the peptidyltransferase step. Decreased outer-membrane permeability and active efflux have been identified in Gram-negative bacteria however, the major resistance mechanism is drug inactivation by chloramphenicol acetyltransferase. This occurs in... 

The gram-negative cell wall contains only a shallow peptidoglycan layer. On the outer side of this layer is the outer membrane, a complex stmcture consisting of four major components phospholipids, lipopolysaccharide, proteins (e.g., porins), and lipoprotein. Lipolysaccharide (endotoxin) is responsible for the pyrogenicity of the gram-negative bacteria. 

Figure 1 Schematic illustration of the supramolecular architecture of the three major classes of prokaryotic cell envelopes containing crystalline bacterial cell surtece layers (S-layers). (a) Cell envelope structure of Gram-negative archaea with S-layers as the only cell wall component external to the cytoplasmic membrane, (b) Cell envelope as observed in Gram-positive archaea and bacteria. In bacteria the rigid wall component is primarily composed of peptidoglycan. In archaea other wall polymers (e.g., pseudomurein or methanochondroitin) are found, (c) Cell envelope profile of Gram-negative bacteria, composed of a thin peptidoglycan layer and an outer membrane. If present the S-layer is closely associated with the lipopolysaccharide of the outer membrane. (Modified after U.B. Sleytr, P. Messner, D. Pum, and M. Sdra. Crystalline Bacterial Cell Surface Proteins. Austin, TX R.G. Landes/Academic Press, 1996. With permission.)...

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