Conduction pore

Industrial carbon anodes and artificial graphites are not a single material but are rather members of a broad family of essentially pure carbon. Fortunately, artificial graphites can be tailored to vary widely in their strength, density, conductivity, pore structure, and crystalline development. These attributes contribute to their widespread applicability. Specific characteristics are imparted to the fmished product by conti ollmg the selection of precursor materials and the method of processing [19]... 

About 78 human genes encoding a variety of K+ channels and auxiliary subunits have been identified (Fig. 1 Table 1). While the K+ channels are diverse, they share with a unique conducting pore highly selective for K+ ions. TheK+ channels ar e tetramers composed of four a subunits that form the conducting pore. On the basis of primary amino acid sequence of a subunit, K+ channels can be classified into three major families (Fig. 2). 

HVA calcium channels are biochemically hetero-oligomeric complexes of five proteins encoded by four gene families (Fig. 1) The ax subunits of 190-250 kDa contain the voltage-sensor, the selectivity filter, the ion-conducting pore, the binding sites for most calcium... 

The aqueous channel down the center of the TI4P4 complex is narrow ( 4 A) and positively charged. This channel could not allow passage of the large TEA ion or an inactivation peptide. So how do these species navigate through the TI4P4 complex to reach the ion conduction pore Or How does the ion pathway connect to the cytoplasm in the words of the reference 16 authors. 

When these acidic residues where mutated to alanine (neutral) or lysine (positive), rates of inactivation were affected. The largest effect took place with the positive amino acid mutation. The authors found that mutations in the inactivation peptide are tied to those in the Tl-Sl linker near the T1 domain in other words, the inactivation peptide must be near the Tl-Sl linker when it inactivates the pore. The conclusion reached is that since the inactivation peptide cannot fit through the center of the TI4P4 complex, it must reach the ion conduction pore through lateral openings above the T1 tetramer. 

Conclusions from the reference 28 review article are as follows (1) Several models backed by experiment place S4 near the groove between adjacent subunits, while the MacKinnon group model places S4 near the periphery of the protein (2) lanthanide-based resonance energy transfer (LRET) places two S4 residues in segments across the tetramer from each other at a distance of 45 A (3) a method based on tethered quaternary ammonium pore blockers places the extracellular ends of the SI and S3 helices further away from the ion conduction pore than the S3-S4 linker, arguing that the S4 helix resides... 

Voltage-gated sodium channels generate the rapid regenerative upstroke of action potentials and hence play a central role in modulation of the firing activity of excitable cells. They form heterotrimeric transmembrane Na+-conducting pores... 

Thermogenin In brown fat, forms proton-conducting pores in inner mitochondrial... 

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