Browsing by Subject "Potassium"
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- PublicationOpen AccessAnalysis of the amount of lost fluids, some blood components and mineral salts in volleyball under hot weather conditions(Universidad de Murcia, Servicio de Publicaciones, 2023) Badwi Shbeeb, Huda; Saeed Almousawi, Suhad Qasim; Mousa Jawad, SundusThe research objective was to study the amount of lost fluids, some blood components and mineral salts in volleyball players under hot weather conditions. The sample of the present study was composed of 12 volleyball players of Al-Sinaa Club (Baghdad, Iraq) in the 2022/2023 season. The variables analyzed in this study were: Heart rate before and after exercise, internal and external body temperature before and after exertion, potassium ion, sodium ion, calcium ion, and the amount of fluid lost (the player's weight) before and after the exercise. The tests were conducted at a temperature between 42-47 degrees Celsius. The maximum anaerobic exercise was performed with volleyball. The results showed that to play volleyball under hot weather conditions (42-47 degrees Celsius) significantly increased the following variables in volleyball players: heart rate, external body temperature, internal body temperature, sodium ion and calcium ion. However, potassium ion significantly decreased. Therefore, training in hot weather has positive physical repercussions. The authors recommend to train in different weather conditions.
- PublicationEmbargoContribution of ion binding affinity to ion selectivity and permeation in KcsA, a model potassium channel(2012-04-17) Renart Pérez, María Lourdes; Montoya Díaz, Estefanía; Fernández Carvajal, Asia María; Molina Gallego, María Luisa; Poveda Larrosa, José Antonio; Encinar Hidalgo, José Antonio; Ayala Torres, Antonio Vicente; Gómez Pérez, Francisco Javier; Morales Calderón, Andrés; González Ros, José Manuel; Bioquímica y Biología Molecular B e InmunologíaIon permeation and selectivity, key features in ion channel function, are believed to arise from a complex ensemble of energetic and kinetic variables. Here we evaluate the contribution of pore cation binding to ion permeation and selectivity features of KcsA, a model potassium channel. For this, we used E71A and M96V KcsA mutants in which the equilibrium between conductive and nonconductive conformations of the channel is differently shifted. E71A KcsA is a noninactivating channel mutant. Binding of K+ to this mutant reveals a single set of low-affinity K+ binding sites, similar to that seen in the binding of K+ to wild-type KcsA that produces a conductive, low-affinity complex. This seems consistent with the observed K+ permeation in E71A. Nonetheless, the E71A mutant retains K+ selectivity, which cannot be explained on the basis of just its low affinity for this ion. At variance, M96V KcsA is a rapidly inactivating mutant that has lost selectivity for K+ and also conducts Na+. Here, low-affinity binding and high-affinity binding of both cations are detected, seemingly in agreement with both being permeating species in this mutant channel. In conclusion, binding of the ion to the channel protein seemingly explains certain gating, ion selectivity, and permeation properties. Ion binding stabilizes greatly the channel and, depending upon ion type and concentration, leads to different conformations and ion binding affinities. High-affinity states guarantee binding of specific ions and mediate ion selectivity but are nonconductive. Conversely, low-affinity states would not discriminate well among different ions but allow permeation to occur.
- PublicationRestrictedProbing the channel-bound shaker B inactivating peptide by stereoisomeric substitution at a strategic tyrosine residue(American Chemical Society, 2003-07-01) Encinar Hidalgo, José Antonio; Fernández Carvajal, Asia María; Poveda Larrosa, José Antonio; Molina Gallego, María Luisa; Albar, J.P.; Gavilanes Franco, Francisco; González Ros, José Manuel; Bioquímica y Biología Molecular B e InmunologíaA synthetic peptide patterned after the sequence of the inactivating ball domain of the Shaker B K+ channel, the ShB peptide, fully restores fast inactivation in the deletion Shaker BΔ6−46 K+ channel, which lacks the constitutive ball domains. On the contrary, a similar peptide in which tyrosine 8 is substituted by the secondary structure-disrupting d-tyrosine stereoisomer does not. This suggests that the stereoisomeric substitution prevents the peptide from adopting a structured conformation when bound to the channel during inactivation. Moreover, characteristic in vitro features of the wild-type ShB peptide such as the marked propensity to adopt an intramolecular β-hairpin structure when challenged by anionic phospholipid vesicles, a model target mimicking features of the inactivation site in the channel protein, or to insert into their hydrophobic bilayers, are lost in the d-tyrosine-containing peptide, whose behavior is practically identical to that of noninactivating peptide mutants. In the absence of high resolution crystallographic data on the inactivated channel/peptide complex, these latter findings suggest that the structured conformation required for the peptide to promote channel inactivation, as referred to above, is likely to be β-hairpin.
- PublicationRestrictedTyrosine phosphorylation of the inactivating peptide of the Shaker B potassium channel: a structural-functional correlate(American Chemical Society, 2002-09-12) Encinar Hidalgo, José Antonio; Fernández Carvajal, Asia María; Molina Gallego, María Luisa; Molina, A.; Poveda Larrosa, José Antonio; Albar, J.P.; López Barneo, José; Gavilanes Franco, Francisco; Ferrer Montiel, Antonio Vicente; González Ros, José Manuel; Bioquímica y Biología Molecular B e InmunologíaA synthetic peptide patterned after the sequence of the inactivating “ball” domain of the Shaker B K+ channel restores fast (N-type) inactivation in mutant deletion channels lacking their constitutive ball domains, as well as in K+ channels that do not normally inactivate. We now report on the effect of phosphorylation at a single tyrosine in position 8 of the inactivating peptide both on its ability to restore fast channel inactivation in deletion mutant channels and on the conformation adopted by the phosphorylated peptide when challenged by anionic lipid vesicles, a model target mimicking features of the inactivation site in the channel protein. We find that the inactivating peptide phosphorylated at Y8 behaves functionally as well as structurally as the noninactivating mutant carrying the mutation L7E. Moreover, it is observed that the inactivating peptide can be phosphorylated by the Src tyrosine kinase either as a free peptide in solution or when forming part of the membrane-bound protein channel as the constitutive inactivating domain. These findings suggest that tyrosine phosphorylation−dephosphorylation of this inactivating ball domain could be of physiological relevance to rapidly interconvert fast-inactivating channels into delayed rectifiers and vice versa.
- PublicationRestrictedUnfolding and refolding in vitro of a tetrameric, a-helical membrane protein: the prokaryotic potassium channel KcsA(American Chemical Society, 2005-10-06) Barrera Olivares, Francisco Nicolás; Renart Pérez, María Lourdes; Molina Gallego, María Luisa; Poveda Larrosa, José Antonio; Encinar Hidalgo, José Antonio; Fernández Carvajal, Asia María; Neira Faleiro, José Luis; González Ros, José Manuel; Bioquímica y Biología Molecular B e Inmunología2,2,2-Trifluoroethanol (TFE) effectively destabilizes the otherwise highly stable tetrameric structure of the potassium channel KcsA, a predominantly α-helical membrane protein [Valiyaveetil, F. I., Zhou, Y., and MacKinnon, R. (2002) Biochemistry 41, 10771−10777]. Here, we report that the effects on the protein structure of increasing concentrations of TFE in detergent solution include two successive protein concentration-dependent, cooperative transitions. In the first of such transitions, occurring at lower TFE concentrations, the tetrameric KcsA simultaneously increases the exposure of tryptophan residues to the solvent, partly loses its secondary structure, and dissociates into its constituent subunits. Under these conditions, simple dilution of the TFE permits a highly efficient refolding and tetramerization of the protein in the detergent solution. Moreover, following reconstitution into asolectin giant liposomes, the refolded protein exhibits nativelike potassium channel activity, as assessed by patch-clamp methods. Conversely, the second cooperative transition occurring at higher TFE concentrations results in the irreversible denaturation of the protein. These results are interpreted in terms of a protein and TFE concentration-dependent reversible equilibrium between the folded tetrameric protein and partly unfolded monomeric subunits, in which folding and oligomerization (or unfolding and dissociation in the other direction of the equilibrium process) are seemingly coupled processes. At higher TFE concentrations this is followed by the irreversible conversion of the unfolded monomers into a denatured protein form.