Cytoplasmic membrane, bacterial transport across

Aminoglycosides are parenteral antibiotics most widely used in the treatment of infections due to enteric gramnegative bacteria. However, aminoglycosides are often used in combination with cell wall-active agents such as beta-lactams or vancomycin for treatment of endocarditis. Aminoglycosides initially diffuse passively across the baae-rial outer membrane and are then actively transported into the cytoplasm. This active transport is inhibited in low pH or anaerobic conditions. Once inside the cytoplasm, aminoglycosides inhibit protein synthesis by binding to the bacterial... 

MECHANISM OF ACTION AND RESISTANCE Tetracyclines inhibit bacterial protein synthesis by binding to the 30S bacterial ribosome and preventing access of aminoacyl tRNAto the acceptor (A) site on the mRNA-ribosome complex (Figure 46-1). They enter gram-negative bacteria by passive diffusion through channels formed by porins in the onter ceU membrane and by active transport that pumps tetracyclines across the cytoplasmic membrane. 

Unphosphorylated functioning according to Fig. 5 catalyzes facilitated diffusion of mannitol across the membrane. The same process has been reported for purified II reconstituted in proteoliposomes [70]. The relevance of this activity in terms of transport of mannitol into the bacterial cell is probably low, but it may have important implications for the mechanism by which E-IIs catalyze vectorial phosphorylation. It would indicate that the transmembrane C domain of Il is a mannitol translocating unit which is somehow coupled to the kinase activity of the cytoplasmic domains. We propose that the inwardly oriented binding site which is in contact with the internal water phase (Ecyt Mtl, see Fig. 5) is the site from where mannitol is phosphorylated when transport is coupled to phosphorylation. Meehan-... 

Poly-(3-hydroxybutanoic acid) (PHB), belongs to the large family of poly-(hydroxyalkanoates) (PHAs), high molecular weight natural polymers produced by various microorganisms and stored in cell cytoplasm (200). Low molecular weight PHB, also present in bacteria and are primarily involved in transport of ions and DNA across inner bacterial membrane (201). PHB could be developed as a valuable biocompatible material with possible applications in gene delivery after cytotoxic, safety, and efficacy evaluations. 

VDAC plays a role in the regulated flux of metabolites—usually anionic species such as phosphate, chloride, organic anions, and the adenine nucleotides—across the outer membrane. VDAC appears to form an open p -barrel structure similar to that of the bacterial porins (Section 12.5.2). although mitochondrial porins and bacterial porins may have evolved independently. Some cytoplasmic kinases bind to VDAC, thereby obtaining preferential access to the exported ATP. In contrast, the inner membrane is intrinsically impermeable to nearly all ions and polar molecules. A large family of transporters shuttles metabolites such as ATP, pyruvate, and citrate across the inner mitochondrial membrane. The two faces of this membrane will be referred to as the matrix side and the cytosolic side (the latter because it is freely accessible to most small molecules in the cytosol). They are also called the N and P sides, respectively, because the membrane potential is negative on the matrix side and positive on the cytosolic side. 

This approach has been adopted to investigate the function of COX from the proteobacterium Rhodohacter sphaeroides [110], the last enzyme in the respiratory electron transport chain of bacteria, located in the bacterial inner membrane. It receives one electron from each of four ferrocytochrome c molecules, located on the periplasmic side of the membrane, and transfers them to one oxygen molecule, converting it into two water molecules. In the process, it binds four protons from the cytoplasm to make water, and in addition translocates four protons from the cytoplasm to the periplasm, to establish a proton electrochemical potential difference across the membrane. In this ptBLM, the orientation of the protein with respect to the membrane normal depends on the location of the histidine stretch... 

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