English Journal

Uptake and metabolic effects of salicylic acid on the pulvinar motor cells of Mimosa pudica L.

Dédaldéchamp F1, Saeedi S2, Fleurat-Lessard P2, Roblin G2.Author information 1Université de Poitiers, EBI UMR CNRS 7267, Equipe Physiologie Moléculaire du Transport des Sucres, 3 rue Jacques Fort, 86022 Poitiers cedex, France. Electronic address: fabienne.dedaldechamp@univ-poitiers.fr.2Université de Poitiers, EBI UMR CNRS 7267, Equipe Physiologie Moléculaire du Transport des Sucres, 3 rue Jacques Fort, 86022 Poitiers cedex, France.AbstractIn this paper, the salicylic acid (o-hydroxy benzoic acid) (SA) uptake by the pulvinar tissues of Mimosa pudica L. pulvini was shown to be strongly pH-dependent, increasing with acidity of the assay medium. This uptake was performed according to a unique affinity system (K(m) = 5.9 mM, V(m) = 526 pmol mgDW(-1)) in the concentration range of 0.1-5 mM. The uptake rate increased with increasing temperature (5-35 °C) and was inhibited following treatment with sodium azide (NaN3) and carbonyl cyanide m-chlorophenylhydrazone (CCCP), suggesting the involvement of an active component. Treatment with p-chloromercuribenzenesulfonic acid (PCMBS) did not modify the uptake, indicating that external thiol groups were not necessary. KCl, which induced membrane depolarization had no significant effect, and fusicoccin (FC), which hyperpolarized cell membrane, stimulated the uptake, suggesting that the pH component of the proton motive force was likely a driving force. These data suggest that the SA uptake by the pulvinar tissues may be driven by two components: an ion-trap mechanism playing a pivotal role and a putative carrier-mediated mechanism. Unlike other benzoic acid derivatives acting as classical respiration inhibitors (NaN3 and KCN), SA modified the pulvinar cell metabolism by increasing the respiration rate similar to CCCP and 2,4-dinitrophenol (DNP). Furthermore, SA inhibited the osmoregulated seismonastic reaction in a pH dependent manner and induced characteristic damage to the ultrastructural features of the pulvinar motor cells, particularly at the mitochondrial level.
Plant physiology and biochemistry : PPB / Société française de physiologie végétale.Plant Physiol Biochem.2014 Jan;74:125-32. doi: 10.1016/j.plaphy.2013.11.010. Epub 2013 Nov 19.
In this paper, the salicylic acid (o-hydroxy benzoic acid) (SA) uptake by the pulvinar tissues of Mimosa pudica L. pulvini was shown to be strongly pH-dependent, increasing with acidity of the assay medium. This uptake was performed according to a unique affinity system (K(m) = 5.9 mM, V(m) = 526 pm
PMID 24292275

Cysteine substitutions define etomidate binding and gating linkages in the α-M1 domain of γ-aminobutyric acid type A (GABAA) receptors.

Stewart DS1, Hotta M, Li GD, Desai R, Chiara DC, Olsen RW, Forman SA.Author information 1From the Department of Anesthesia Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts 02114.AbstractEtomidate is a potent general anesthetic that acts as an allosteric co-agonist at GABAA receptors. Photoreactive etomidate derivatives labeled αMet-236 in transmembrane domain M1, which structural models locate in the β+/α- subunit interface. Other nearby residues may also contribute to etomidate binding and/or transduction through rearrangement of the site. In human α1β2γ2L GABAA receptors, we applied the substituted cysteine accessibility method to α1-M1 domain residues extending from α1Gln-229 to α1Gln-242. We used electrophysiology to characterize each mutant's sensitivity to GABA and etomidate. We also measured rates of sulfhydryl modification by p-chloromercuribenzenesulfonate (pCMBS) with and without GABA and tested if etomidate blocks modification of pCMBS-accessible cysteines. Cys substitutions in the outer α1-M1 domain impaired GABA activation and variably affected etomidate sensitivity. In seven of eight residues where pCMBS modification was evident, rates of modification were accelerated by GABA co-application, indicating that channel activation increases water and/or pCMBS access. Etomidate reduced the rate of modification for cysteine substitutions at α1Met-236, α1Leu-232 and α1Thr-237. We infer that these residues, predicted to face β2-M3 or M2 domains, contribute to etomidate binding. Thus, etomidate interacts with a short segment of the outer α1-M1 helix within a subdomain that undergoes significant structural rearrangement during channel gating. Our results are consistent with in silico docking calculations in a homology model that orient the long axis of etomidate approximately orthogonal to the transmembrane axis.
The Journal of biological chemistry.J Biol Chem.2013 Oct 18;288(42):30373-86. doi: 10.1074/jbc.M113.494583. Epub 2013 Sep 5.
Etomidate is a potent general anesthetic that acts as an allosteric co-agonist at GABAA receptors. Photoreactive etomidate derivatives labeled αMet-236 in transmembrane domain M1, which structural models locate in the β+/α- subunit interface. Other nearby residues may also contribute to etomidate
PMID 24009076

Mutation of a single amino acid converts the human water channel aquaporin 5 into an anion channel.

Qin X1, Boron WF.Author information 1Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio.AbstractAquaporin 6 (AQP6) is unique among mammalian AQPs in being an anion channel with negligible water permeability. However, the point mutation Asn60Gly converts AQP6 from an anion channel into a water channel. In the present study of human AQP5, we mutated Leu51 (corresponding to residue 61 in AQP6), the side chain of which faces the central pore. We evaluated function in Xenopus oocytes by two-electrode voltage clamp, video measurements of osmotic H2O permeability (Pf), microelectrode measurements of surface pH (pHS) to assess CO2 permeability, and surface biotinylation. We found that AQP5-L51R does not exhibit the H2O or CO2 permeability of the wild-type protein but instead has a novel p-chloromercuribenzene sulfonate (pCMBS)-sensitive current. The double mutant AQP5-L51R/C182S renders the conductance insensitive to pCMBS, demonstrating that the current is intrinsic to AQP5. AQP5-L51R has the anion permeability sequence I(-) > NO3(-) ≅ NO2(-) > Br(-) > Cl(-) > HCO3(-) > gluconate. Of the other L51 mutants, L51T (polar uncharged) and L51V (nonpolar) retain H2O and CO2 permeability and do not exhibit anion conductance. L51D and L51E (negatively charged) have no H2O or CO2 permeability. L51K (positively charged) has an intermediate H2O and CO2 permeability and anion conductance. L51H is unusual in having a relatively low CO2 permeability and anion conductance, but a moderate Pf. Thus, positively charged mutations of L51 can convert AQP5 from a H2O/CO2 channel into an anion channel. However, the paradoxical effect of L51H is consistent with the hypothesis that CO2, in part, takes a pathway different from H2O through AQP5.
American journal of physiology. Cell physiology.Am J Physiol Cell Physiol.2013 Sep 15;305(6):C663-72. doi: 10.1152/ajpcell.00129.2013. Epub 2013 Jul 10.
Aquaporin 6 (AQP6) is unique among mammalian AQPs in being an anion channel with negligible water permeability. However, the point mutation Asn60Gly converts AQP6 from an anion channel into a water channel. In the present study of human AQP5, we mutated Leu51 (corresponding to residue 61 in AQP6), t
PMID 23842530

Japanese Journal

Functional Characterization of the Carrier-Mediated Transport System for Glycerol in Everted Sacs of the Rat Small Intestine(Biopharmacy)

Biological & pharmaceutical bulletin 27(11), 1826-1830, 2004-11-01
NAID 110003608705

デルフィニウム切り花の萎れに伴う糖代謝酵素活性の変動

園芸学会雑誌 72(1), 37-42, 2003-01-15
NAID 110001803395

Inhibition of a Cl^--Transporting P-type ATPase in Aplysia Gut(Physiology)

Zoological science 18(1), 17-19, 2001-01-20
NAID 110003371897

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★リンクテーブル★

リンク元	「p-クロロ水銀フェニルスルホン酸」「chloromercuribenzenesulfonate」「pCMPS」「4-chloromercuribenzenesulfonate」「p-chloromercuribenzenesulfonate」