Transporter complexes

Complex ions used for electroplating are anions. The cathode tends to repel them, and their transport is entirely by diffusion. Conversely, the field near the cathode assists cation transport. Complex cyanides deserve some elaboration in view of their commercial importance. It is improbable that those used are covalent co-ordination compounds, and the covalent bond breaks too slowly to accommodate the speed of electrode reactions. The electronic structure of the cyanide ion is ... 

Complexes III and IV have Fe-porphyrin prosthetic groups (hemes), complex IV also contains copper atoms which are involved in electron transport. Complexes I, III, and IV use the energy of electron transport to pump protons out of the matrix so as to maintain a pH gradient and an electrical potential difference across the inner membrane required for ATP synthesis (see below and Appendix 3). It is important to remember that all dehydrogenations of metabolic substrates remove two protons as well as two electrons and that a corresponding number of protons are consumed in the final reduction of dioxygen (Figures 5, 6). 

As seen above (equation (5)), the basis of the simple bioaccumulation models is that the metal forms a complex with a carrier or channel protein at the surface of the biological membrane prior to internalisation. In the case of trace metals, it is extremely difficult to determine thermodynamic stability or kinetic rate constants for the adsorption, since for living cells it is nearly impossible to experimentally isolate adsorption to the membrane internalisation sites (equation (3)) from the other processes occurring simultaneously (e.g. mass transport complexation adsorption to other nonspecific sites, Seen, (equation (31)) internalisation). 

Transport of procollagen molecules from the ER to the Golgi was shown to occur in transport complexes and it... 

Function and Assembly of Electron-Transport Complexes in Desulfovibrio vulgaris Hildenborough... 

The path that leads from full sized protein to epitopes at the cell surface is complex, consisting of the generation of small peptides, translocation of the peptides to the endoplasmic reticulum by a transporter complex, loading of the peptides onto MHC class-I molecules and relocation of the MHC class-I-peptide complex to the cell surface (Rock and Goldberg, 1999). Since many of these steps are known to be prime targets for viral evasion strategies, the next step was to identify at what point the GAr interferes with the presentation of EBNAl. 

A Transport inhibitors bind to one of the electron transport complexes and block the transfer of electrons to oxygen, thus interfering with the ability to create a proton gradient (Table 7-2). 

Conrad, H. E., K. Lieb, and I. C. Gunsalus, Mixed function oxidation. III. An electron transport complex in camphor ketolactonization , J. Biol. Chem., 240,4029-4037 (1965). 

The mechanism of oxidation of NADH in the electron transport chain appears to occur by transfer of a hydrogen atom together with two electrons (a hydride ion H ). Oxidation of FADH2 to FAD might occur by transfer of two hydrogen atoms or by transfer of H + H+. However, it is useful to talk about all of these compounds as electron carriers with the understanding that movement of one or both of the electrons may be accompanied by transfer of H+. The electron transport complex is pictured in a very simplified form in Fig. 10-5. 

These complexes are usually named as follows I, NADH-ubiquinone oxidoreductase II, succinate-ubiquinone oxidoreductase III, ubiquinol-cytochrome c oxidoreductase IV, cytochrome c oxidase. The designation complex V is sometimes applied to ATP synthase (Fig. 18-14). Chemical analysis of the electron transport complexes verified the probable location of some components in the intact chain. For example, a high iron content was found in both complexes I and II and copper in complex IV. 

What are the structures of the individual electron transport complexes What are the subunit compositions What cofactors are present How are electrons transferred How are protons pumped We will consider these questions for each of complexes I-IV, as found in both prokaryotes and eukaryotes.88d e... 

What chemical properties are especially important for the following compounds in the electron transport complexes of mitochondria ... 

The significance, if any, of these complexes in sugar transport is not yet understood. The specificity pattern however has some suggestive correlations with those observed for transport, and the complexes may have some secondary role in determining the overall specificity (similar to that perhaps played by the hypothetical transporter or T substance of Figure 2) in the overall proposed scheme for the permease system. Considered in this sense the primary specificity of the system would be determined by the permease protein (P) in accelerating the formation of the substrate-transporter complex, but the overall specificity of the system would reflect the properties of all components. 

According to the chemiosmotic theory, flow of electrons through the electron-transport complexes pumps protons across the inner membrane from the matrix to the intermembrane space. This raises the pH in the matrix and leaves the matrix negatively charged with respect to the intermembrane space and the cytosol. Protons flow passively back into the matrix through a channel in the ATP-synthase, and this flow drives the formation of ATP. 

Unesterified fatty acids are carried in plasma by albumin (chapter 18). The plasma also transports more complex lipids (cholesterol, triacylglycerols) among the various tissues as components of lipoproteins (spherical particles composed of lipids and proteins). Because cholesterol and triacylglyc-erol are insoluble in an aqueous medium such as the plasma, these lipoproteins (which are soluble in plasma) have evolved for the purpose of transporting complex lipids among tissues. In this section we are concerned with the structure and metabolism of these lipoproteins. 

Serotonin accumulation, as well as other biogenic amines in neuronal tissues, adds an additional order of complexity to ion coupled transport and accumulation. Three different monovalent ions appear to be involved in the formation of a functional serotonin transport complex. External Na+ and Cl- as well as internal K+ are involved in serotonin uptake (Kanner, 1983 Graham and Langer, 1992). In this system the rapid relocation of the empty carrier is presumed to be the role for K+. No experimental verification of this exists. 

In the ATP synthesis reaction, catalyzed by the transporter complex FoFi-ATPase, nA H+ ions are transported from the intermembrane space to the matrix ... 

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