Bacterial membranes proteins

The three-dimensional structure of the bacterial membrane protein, bac-teriorhodopsin, was the first to be obtained from electron microscopy of two-dimensional crystals. This method is now being successfully applied to several other membrane-bound proteins. 

When the new term permease was coined to designate bacterial membrane proteins specialized in the transport of specific metabolites [1,2], it covered a concept which was not quite new. The existence of membrane transport systems had been demonstrated in animal tissues by Cori as early as 1925 (see [3]). However, the discovery and characterization of permeases in bacteria revolutionized prospects for studying the properties of transport systems, opening the way to a new field and a very fruitful methodology. 

Koronakis, V., Sharff, A., Koronakis, E., Luisi, B. and Hughes, C. (2000). Crystal structure of the bacterial membrane protein TolC central to multidrug efflux and protein export, Nature, 405, 914—919. 

Fig. 5.3. Structure of the OmpF porin of E. coli. The porin is a bacterial membrane protein with P-sheet structures as transmembrane elements. The structure of a monomer of the OmpF porin is shown. In total, 16 P-bands are configured in the form of a cylinder and form the waUs of a pore through which selective passage of ions takes place. LI—L8 are long loops, Tl,2,3 and T7,8 are short bends (T turn) that fink the P-sheets. According to Cowan et al. (1992), with per-...

TINS Proof of Principle Application to a Bacterial Membrane Protein... 

Development of a High-affinity Inhibitor of Bacterial Membrane Protein DsbB Using TINS... 

Figure 6.7 Ligand screening of a bacterial membrane protein. (A) The structure of Ubiquinone-5 used to asses the integrity of immobilized Dsbfi during the screen. (B) Ubiquinone-5 binding to immobilized DsbB during the screen. Binding is defined as in Rgure 6.5. (C) Tnzyme inhibition curve of a hit from the screen.

Figure 1 Examples of several bacterial membrane proteins. The outer membrane (OM) of Gram-negative bacteria contains exclusively fS-barrel proteins, and three examples are shown BtuB (PDB ID 1NQF), which is the 22 p-stranded TonB-dependent active transporter for vitamin B 2/ th LamB or maltoporin trimer (PDB ID 1AF6), which is the 18 p-stranded passive sugar transporter and OmpA (PDB ID 1BXW), which is an 8 p-stranded protein that provides structural support for the OM. Proteins in the cytoplasmic membrane (CM) are helical, and three examples are shown the potassium channel KcsA (PDB ID 1BL8), which is a tetramer Sec YEG (PDB ID 1RH5), which forms the protein transport channel in Methanococcus and BtuCD (PDB ID ...

Taken together, these results strongly support the notion that mAChRs and, most hkely, other GPCRs [21] are composed of multiple (rather than only two) individually stable, autonomous folding domains. The folding and assembly of GPCRs therefore appears to occur via a two-step mechanism, similar to that previously described for the bacterial membrane protein, bacteriorhodopsin [22]. In step I, individually stable folding units are established across the hpid bilayer in step II, these domains interact with each other to form functional receptor complexes. 

Bacteria (red) are stained with an antibody specific for a bacterial membrane protein that binds cellular profilin and is essential for infectivity and motility. Behind each bacterium is a "tail" of actin (green) stained with fluorescent phalloidin. Numerous bacterial cells move independently within the cytosol of an infected mammalian cell. Infection is transmitted to other cells when a spike of cell membrane, generated by a bacterium, protrudes into a neighboring cell and is engulfed by a phagocytotic event. 

Rare exceptions are bacterial membrane proteins, which contain a few D-Amino Acids, modified amino acids - primarily lysine (see here) and proline (see here), and occasional incorporation of the rare amino acid, selenocysteine). 

Bacteriorhodopsin is an integral bacterial membrane protein. As seen in Figure 10.15, the linear polypeptide chain of bacteriorhodopsin folds back and forth several times in the membrane to provide a channel through which protons move. Figure 10.16 shows that a plot of the hydrophobic tendency of amino acids in the protein parallels the regions embedded in the membrane. Thus, hydrophobic regions of the protein are embedded in the protein and hydrophilic regions are at the surfaces. 

Lysolipids have also proven useful for direct resolubilization of membrane proteins from cell-free expression pellets for solution NMR structure determination, as was illustrated for three bacterial membrane proteins [88]. However, these structures were all characterized by loose helical packing, which may reflect a destabilizing influence of LMPG on these proteins. Alternatively, the loose structures could have been a consequence of the type and number of structural restraints used, leaving unanswered the question of possible denaturing effects of this detergent on these stmctures. 

Van-der-Werf, R and Koshland, D.E., Jr. (1977). Identification of a y-glutamyl methyl ester in bacterial membrane protein involved in chemotaxis. y. Biol. Chem. 252, 2793-2795. 

Attention is focused on carotenoids and polyenes, which are known to be chemically very unstable as isolated entities but to acquire great stability when they are suitably surrounded by a protein cage and become the active elements in the mechanism of vision and photosynthesis. The CL dependence of the in situ Raman spectra of the carotenoids as naturally occurring pigments in bird feathers was studied by Veronelli et al. [65]. Later attention was focused on the bacterial membrane protein bacteriorhodopsin (bR). a small protein (—26,000 daltons) whose potential application in optical and electro-optical devices has been explored by many authors. The justification of such interest lies in the fact that bR contains all-/rfl/ .v retinal, which acts as a lightabsorbing center and makes bR a naturally reversible photochromic system. All-optical switching can be achieved by proper illumination of bR with yellow or blue light. 

S. T. Islam and J. S. Lam, Topological Mapping Methods for is a-Helical Bacterial Membrane Proteins-an Update and a Guide, MicrobiologyOpen, 2013, 2, 350. 

NMR techniques were also used to study bacterial membrane proteins and protein complexes, such as the twin-arginine transport (Tat) system identified in bacteria, as well as in plant chloroplasts, as a unique system that transports proteins across membranes in their fully-folded states. ... 

We have been interested in the regulation of the synthesis of membrane proteins and lipids. In particular, we have tried to answer several questions Are bacterial membrane proteins synthesized in the absence of lipid synthesis Are these proteins, if synthesized, integrated into the membrane If the proteins are integrated into the membrane, can they function when introduced in the absence of lipid synthesis These questions have been probed with bacterial mutants auxotrophic for glycerol, an essential constituent of all major classes of phospholipids. 

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