Protein Transport Pathways

Bryant, N., and Stevens, T. (1998). Vacuole biogenesis in Saccharomyces cerevisiae protein transport pathway to the yeast vacuole. Microbiol. Mol. Biol. Rev. 62, 230—247. 

Creighton, A. M., Hulford, A., Mant, A., Robinson, D. and Robinson, C. (1995) A monomeric, tightly folded stromal intermediate on the delta pH-dependent thylakoidal protein transport pathway./. Biol. Cbem., 270, 1663-9. 

A child can die because of this single defect in one of the many machines needed for taking proteins to the lysosome. A single flaw in the cell s labyrinthine protein-transport pathway is fatal. Unless the entire system were immediately in place, our ancestors would have suffered a similar fate. Attempts at a gradual evolution of the protein transport system are a recipe for extinction. 

Molik, S., Karnauchov, I., Weidlich, C., Herrmann, R. G., and Klosgen, R. B. (2001). The Rieske Fe/S protein of the cytochrome be,// complex in chloroplasts missing link in the evolution of protein transport pathways in chloroplasts J. Biol. Chem. 276, 42761-42766. 

Secretory protein translocation. See Stephenson, K Sec-dependent protein translocation across biological membranes. Evolutionary conservation of an essential protein transport pathway. Mol. Membrane Biol. 22,17-28, 2005. 

A hypothesis for the oxidation of purines in the presence of this enzyme has been elaborated by Bergmann and his colleagues. It postulates that the purine, often in one of its less prevalent tautomeric forms, is adsorbed on the protein, or the riboflavin coenzyme, of the enzyme then hydration occurs under the influence of the electronic field of the enz5rme, and this must involve a group that is not sterically blocked by the enzyme but which is accessible to the electron-transport pathway of the riboflavin moiety. Finally, the secondary alcohol is assumed to be dehydrogenated in this pathway to give a doubly... 

The transport behavior of Li+ across membranes has been the focus of numerous studies, the bulk of which have concentrated upon the human erythrocyte for which the Li+ transport pathways have been elucidated and are summarized below. The movement of Li+ across cell membranes is mediated by transport systems which normally transport other ions, therefore the normal intracellular and subcellular electrolyte balance is likely to be disturbed by this extra cation. Additionally, Li+ has been shown to increase membrane phospholipid unsaturation in rat brain, leading to enhanced fluidity in the membrane, which could have repercussions for membrane-associated proteins and for membrane transport properties. 

Le Borgne, R., and Hoflack, B. (1998a). Mechanisms of protein sorting and coat assembly insights from the clathrin-coated vesicle pathway. Curr. Opin. Cell Biol. 10, 499-503. Le Borgne, R., and Hoflack, B. (1998b). Protein transport from the secretory to the endocytic pathway in mammalian cells. Biochim. Biophys. Acta 1404, 195-209. 

From the Golgi apparatus, the proteins are transported by vesicles to various targets in the cells—e.g., to lysosomes (4), the plasma membrane (6), and secretory vesicles (5) that release their contents into the extracellular space by fusion with the plasma membrane (exocytosis see p. 228). Protein transport can either proceed continuously (constitutive), or it can be regulated by chemical signals. The decision regarding which pathway a protein... 

Secretory pathway. Ribosomes that synthesize a protein with a signal peptide for the ER settle on the ER (see p. 228). The peptide chain is transferred into the lumen of the rER. The presence or absence of other signal sequences and signal regions determines the subsequent transport pathway. 

Results obtained from the partial reactions, chlorophyll fluorescence, and binding studies did not provide any clues relative to interactive sites on the electron-transport pathway for the allelochemicals. No evidence was obtained to specifically implicate Interference with the protein of PS II. Additionally, insofar as they could be analyzed, none of the allelochemicals affected PS I-associated electron transport between the site of donation by DPIPH and acceptance by methyl vlologen. 

HDL may be taken up in the liver by receptor-mediated endocytosis, but at least some of the cholesterol in HDL is delivered to other tissues by a novel mechanism. HDL can bind to plasma membrane receptor proteins called SR-BI in hepatic and steroidogenic tissues such as the adrenal gland. These receptors mediate not endocytosis but a partial and selective transfer of cholesterol and other lipids in HDL into the cell. Depleted HDL then dissociates to recirculate in the bloodstream and extract more lipids from chylomicron and VLDL remnants. Depleted HDL can also pick up cholesterol stored in extrahepatic tissues and carry it to the liver, in reverse cholesterol transport pathways (Fig. 21-40). In one reverse transport path, interaction of nascent HDL with SR-BI receptors in cholesterol-rich cells triggers passive movement of cholesterol from the cell surface into HDL, which then carries it back to the liver. In a second pathway, apoA-I in depleted HDL in-... 

The uptake of potassium by microorganisms has been well studied. In the case of E. coli, kinetic investigations on different strains have demonstrated the presence of three or four transport systems. The presence of inducible pathways with widely different Km values for binding K+ allows the cell to accumulate K+ to a constant level under different environments. These transport pathways include those linked to the proton circuit and an example linked to a pump and ATP hydrolysis. Thus the Kdp system is a high affinity pathway with Km = 1 mol dm-3, and involves three proteins in the inner membrane of E. coli, including a K+-stimulated membrane ATPase. The KHA (i.e. K+-H+ antiport) path is driven by proton motive force, while the low affinity system TrKA depends on both ATP and the proton motive force.80,81,82 S. cerevisiae accumulates K+ by K+/H+ exchange.83 Potassium transport may thus be used to control intracellular pH. 

Thermogenic systems based on uncoupling proteins or on the alternative electron transport pathways found in mitochondria of certain plants represent what in many ways is the sim-... 

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