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We report the assignment of the 110 amino acid second calponin homology domain of human α-actinin-4. The two calponin homology
domains of α-actinin combine to regulate F-actin binding. 相似文献
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Escherichia coli grown anaerobically for osmotic studies upon increased osmolarity in alkaline medium carried out H+–K+-exchange in two steps, the first of which was DCCD1 sensitive and osmo-dependent and had the 2H+/K+ stoichiometry. H+-efflux in the presence of protonophore (CCCP) upon increase of osmolarity was shown to be high and inhibited by DCCD, whereas H+-efflux induced by a decrease of osmolarity was small and not inhibited by DCCD. The 2H+/K+-exchange was absent intrkA anduncA mutants. InuncB mutant 2H+/K+-exchange was not DCCD-and osmosensitive. Competition between DCCD and osmoshock on inhibition of 2H+/K+-exchange was found. Osmosensitivity of this exchange disappeared in spheroplasts. Osmosensitivity of both 2H+/K+-exchange and the F0F1 and osmoregulation of the F0F1 via F0 and a periplasmic space are postulated.Abbreviations F0F1
H+-ATPase complex
- F0
H+-channel, proteolipid
- F1
H+-ATPase
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Trk
constitutive system for K+ uptake
- PV
periplasmic protein valve
- DCCD
N,N-dicyclohexylcarbodiimide
- CCCP
carbonylcyanide-m-chlorophenylhydrazone
- H or K
transmembrane electrochemical gradient for H+ or K+ respectively
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membrane potential
- upshock or downshock
increase or decrease of medium osmolarity, respectively
- CGSC
E. coli Genetic Stock Center, Yale University, USA 相似文献
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Koichi Niwa Osamu Inanami Tohru Yamamori Toshio Ohta Taku Hamasu Takeshi Karino 《Free radical research》2013,47(11):1147-1153
To clarify the signaling pathways of oxidative stress-induced apoptosis in bovine aortic endothelial cells (BAEC), we treated cells with 1 mM H 2 O 2 and investigated the roles of protein kinase C i (PKC i ) and Ca 2+ in the accumulation of p53 associated with apoptosis. The treatment of cells with H 2 O 2 caused the accumulation of p53, which was inhibited by rottlerin (a PKC i inhibitor) but not by BAPTA-AM (an intracellular Ca 2+ chelator). PKC i itself was activated through the phosphorylation at tyrosine residues. H 2 O 2 induced the release of cytochrome c and the activation of caspases 3 and 9, and these apoptotic signals were inhibited by rottlerin and BAPTA-AM. These results suggest that PKC i contributes to the accumulation of p53 and that Ca 2+ plays a role in downstream signals of p53 leading to apoptosis in H 2 O 2 -treated BAEC. 相似文献
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《Inorganica chimica acta》1986,117(1):45-48
The resonance Raman spectra of K2(Ti(O2)(SO4)2)·5H2O and K2(Ti(O2)(C2O4)2)·3H2O are recorded. The results are consistent with the triangular structure of the peroxotitanium unit, Ti(O2), with C2ν symmetry. The ν(OO), νs(TiO) and νas(TiO) are observed around 890, 610 and 535 cm−1, respectively. The resonance effects are shown to be associated with the 425 nm absorption band. This band is assigned to the O22− → Ti(IV) charge-transfer transition. The calculated force constant values for the O22− and TiO bonds are 320 and 275 N m−1, respectively. 相似文献
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Nitrogen fixation in excised root nodules of 2-year-old, postfireCeanothus tomentosus andC. leucodermis seedlings was measured over an 8-month period using the acetylene reduction method. High levels of NO3–N and NH4–N present in postfire soils were limited to the upper 10 cm and did not inhibit nodulation in these deeper-rooting seedlings. Decreases in acetylene reduction activity occurred with decreased soil moisture and increased soil temperature. Nitrogen gains from these two Ceanothus shrub seedlings totalled 1.6 kg N ha–1 yr–1. 相似文献
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Precise regulation of the intracellular concentration of chloride [Cl?]i is necessary for proper cell volume regulation, transepithelial transport, and GABA neurotransmission. The Na–K–2Cl (NKCCs) and K–Cl (KCCs) cotransporters, related SLC12A transporters mediating cellular chloride influx and efflux, respectively, are key determinants of [Cl?]i in numerous cell types, including red blood cells, epithelial cells, and neurons. A common “chloride/volume-sensitive kinase”, or related system of kinases, has long been hypothesized to mediate the reciprocal but coordinated phosphoregulation of the NKCCs and the KCCs, but the identity of these kinase(s) has remained unknown. Recent evidence suggests that the WNK (with no lysine = K) serine–threonine kinases directly or indirectly via the downstream Ste20-type kinases SPAK/OSR1, are critical components of this signaling pathway. Hypertonic stress (cell shrinkage), and possibly decreased [Cl?]i, triggers the phosphorylation and activation of specific WNKs, promoting NKCC activation and KCC inhibition via net transporter phosphorylation. Silencing WNK kinase activity can promote NKCC inhibition and KCC activation via net transporter dephosphorylation, revealing a dynamic ability of the WNKs to modulate [Cl?]. This pathway is essential for the defense of cell volume during osmotic perturbation, coordination of epithelial transport, and gating of sensory information in the peripheral system. Commiserate with their importance in serving these critical roles in humans, mutations in WNKs underlie two different Mendelian diseases, pseudohypoaldosteronism type II (an inherited form of salt-sensitive hypertension), and hereditary sensory and autonomic neuropathy type 2. WNKs also regulate ion transport in lower multicellular organisms, including Caenorhabditis elegans, suggesting that their functions are evolutionarily-conserved. An increased understanding of how the WNKs regulate the Na–K–2Cl and K–Cl cotransporters may provide novel opportunities for the selective modulation of these transporters, with ramifications for common human diseases like hypertension, sickle cell disease, neuropathic pain, and epilepsy. 相似文献
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J.R. Flores 《Molecular simulation》2013,39(4):325-333
Further trajectory studies on the C+ + H2O reaction have been performed using a potential energy surface described through a finite element method in its p version. In former trajectory studies [Y. Ishikawa, T. Ikegami and R.C. Binning Jr., Direct ab initio molecular dynamics study of C++H2O: angular distribution of products and distribution of product kinetic energies, Chem. Phys. Lett. 370 (2003), pp. 490–495; J.R. Flores, Quasichemical trajectories on a finite element density functional potential energy surface: the C++H2O reaction revisited, J. Chem. Phys. 125 (2006), 164309], tunnelling was not taken into account. The present results together with the analysis of the electronic excited states [J.R. Flores and A.B. González, The role of the excited electronic states in the C++H2O reaction, J. Chem. Phys. 128 (2008), 144310] are useful to interpret the mechanism of the title reaction, which has been the subject of crossed beam experiments [D.M. Sonnenfroh, R.A. Curtiss and J.M. Farrar, Collision complex formation in the reaction of C+ with H2O, J. Chem. Phys. 83 (1985), pp. 3958–3964] and can be considered a prototypical ion–molecule reaction. 相似文献
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Jian-feng Guo Wen-jing Shi Fu-de Ren Duan-lin Cao Yuan-sheng Zhang 《Journal of molecular modeling》2013,19(8):3153-3163
The DFT-B3LYP/6-311++G(3df,2p) and MP2(full)/6-311++G(3df,2p) calculations were carried out on the binary complex formed by HM (M?=?Li, Na, K) and HF or the π-electron donor (C2H2, C2H4, C6H6), as well as the ternary system FH???HM???C2H2/C2H4/C6H6. The cooperativity effect between the dihydrogen-bonding and H–M???π interactions was investigated. The result shows that the equilibrium distances R H???H and R M???π in the ternary complex decrease and both the H???H and H–M???π interactions are strengthened when compared to the corresponding binary complex. The cooperativity effect of the dihydrogen bond on the H–M???π interaction is more pronounced than that of the M???π bond on the H???H interaction. Furthermore, the values of cooperativity effect follow the order of FH???HNa???π?>?FH???HLi???π?>?FH???HK???π and FH???HM???C6H6?>?FH???HM???C2H4?>?FH???HM???C2H2. The nature of the cooperativity effect was revealed by the analyses of the charge of the hydrogen atoms in H???H moiety, atom in molecule (AIM) and electron density shifts methods. Figure
Shifts of electron density upon ternary-complex formation indicate the cooperativity effect between the dihydrogen-bonding and H–M???π interactions 相似文献
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Idun Dale Rein Caroline Stokke Marwa Jalal June H Myklebust Sebastian Patzke Trond Stokke 《Cell cycle (Georgetown, Tex.)》2015,14(20):3261-3269
Induction of DNA double strand breaks leads to phosphorylation and focus-formation of H2AX. However, foci of phosphorylated H2AX (γH2AX) appear during DNA replication also in the absence of exogenously applied injury. We measured the amount and the number of foci of γH2AX in different phases of the cell cycle by flow cytometry, sorting and microscopy in 4 malignant B-lymphocyte cell lines. There were no detectable γH2AX and no γH2AX-foci in G1 cells in exponentially growing cells and cells treated with PARP inhibitor (PARPi) for 24 h to create damage and reduce DNA repair. The amount of γH2AX increased immediately upon S phase entry, and about 10 and 30 γH2AX foci were found in mid-S phase control and PARPi-treated cells, respectively. The γH2AX-labeled damage caused by DNA replication was not fully repaired before entry into G2. Intriguingly, G2 cells populated a continuous distribution of γH2AX levels, from cells with a high content of γH2AX and the same number of foci as S phase cells (termed “G2H” compartment), to cells that there were almost negative and had about 2 foci (termed “G2L” compartment). EdU-labeling of S phase cells revealed that G2H was directly populated from S phase, while G2L was populated from G2H, but in control cells also directly from S phase. The length of G2H in particular increased after PARPi treatment, compatible with longer DNA-repair times. Our results show that cells repair replication-induced damage in G2H, and enter mitosis after a 2–3 h delay in G2L. 相似文献
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Is the K permeability of the resting membrane controlled by the excitable K channel? 总被引:2,自引:0,他引:2
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D C Chang 《Biophysical journal》1986,50(6):1095-1100
To test whether or not the potassium permeability of the resting membrane is controlled by the excitable K channels (delayed rectifier), we examined changes in the Na and K permeability ratio, PNa/PK, of the squid axon before and after the excitable K channels were blocked. The blockage of the K channels was accomplished by three independent methods: internal application of tetraethylammonium, internal application of 4-aminopyridine plus Cs, and prolong internal perfusion of NaF solution. The permeability ratio was determined using two different methods: the conventional electrophysiological method and a new method based on the measurements of the hyperpolarizing effect of Na removal. We found that blocking the K channels did not cause a proportional decrease in the K permeability of the resting membrane, suggesting that the semipermeable property of the resting membrane is not determined by the excitable K channels. 相似文献
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An ab initio computational density functional theory (DFT) was used to study the formation of the first cyclic molecule (phenyl)
initiated by the ethynyl radical (C2H•). The study covers a competition reaction between the addition reactions of C2H• with ethyne (C2H2) and some molecular re-arrangement schemes. The minimum energy paths of the preferred cyclic formation route were characterized.
A thorough thermochemical analysis was performed by evaluating the differences in the energy of activation (ΔE), enthalpy
(ΔH), and Gibb's free energy (ΔG) of the optimized stable and transition state (TS) molecules. The reaction temperatures were
set to normal (T = 298 K) and combustion (T = 1,200 K) conditions.
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Romero M. SantiagoEmail: |
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