Glutamate 172, essential for modulation of L247T α7 ACh receptors by Ca2+, lines the extracellular vestibule

2002 ◽  
Vol 283 (5) ◽  
pp. C1454-C1460 ◽  
Author(s):  
Donnie Eddins ◽  
Adrian D. Sproul ◽  
Lisa K. Lyford ◽  
James T. McLaughlin ◽  
Robert L. Rosenberg
Keyword(s):  
Crystal Structure ◽  
Divalent Cation ◽  
Lymnaea Stagnalis ◽  
Binding Protein ◽  
Divalent Cations ◽  
Receptor Activity ◽  
Ion Permeation ◽  
Ach Receptors

Neuronal α7 nicotinic ACh receptors (nAChRs) are permeable to and modulated by Ca2+, Ba2+, and Sr2+. These permeant divalent cations interact with slowly desensitizing L247T α7nAChRs to increase the potency and maximal efficacy of ACh, increase the efficacy of dihydro-β-erythroidine (DHβE), and increase agonist-independent activity. Mutation of glutamate 172 (E172) to glutamine or cysteine eliminated these effects of permeant divalent cations. 2-(Trimethylammonium)ethyl methanethiosulfonate (MTSET), a cysteine-modifying reagent directed at water-accessible thiols, inhibited ACh-evoked currents of E172C/L247T α7 nAChRs by >90%, demonstrating that E172 was accessible to permeant ions. The data are consistent with a model of α7receptors, derived from the crystal structure of the ACh binding protein (AChBP) from Lymnaea stagnalis, in which E172 projects toward the lumen of the extracellular vestibule. The observations that E172 was essential for divalent cation modulation of L247T α7 nAChRs and was accessible to permeating ions suggest that this residue participates in coupling ion permeation with modulation of receptor activity.

scholarly journals Bacillus subtilis Cells Lacking Penicillin-Binding Protein 1 Require Increased Levels of Divalent Cations for Growth

1998 ◽  
Vol 180 (17) ◽  
pp. 4555-4563 ◽  
Author(s):  
Thomas Murray ◽  
David L. Popham ◽  
Peter Setlow
Keyword(s):  
Bacillus Subtilis ◽  
Cell Growth ◽  
Divalent Cation ◽  
Vegetative Growth ◽  
Binding Protein ◽  
Divalent Cations ◽  
Penicillin Binding Protein ◽  
Wild Type ◽  
Deficient Medium ◽  
Spore Outgrowth

ABSTRACT Bacillus subtilis strains lacking penicillin-binding protein 1 (PBP1), encoded by ponA, required greater amounts of Mg2+ or Ca2+ for vegetative growth or spore outgrowth than the wild-type strain and strains lacking other high-molecular-weight (HMW) PBPs. Growth of ponA cells in a medium low in Mg2+ also resulted in greatly increased cell bending compared to wild-type cells or cells lacking other HMW PBPs. The addition of high levels of Mg2+ to growth media eliminated these phenotypes of a ponA mutant. In contrast to the effects of divalent cations, NaCl did not restoreponA cell growth in a divalent-cation-deficient medium. Surprisingly, wild-type cells swelled and then lysed during both vegetative growth and spore outgrowth when 500 mM NaCl was included in a divalent-cation-deficient medium. Again, Mg2+ addition was sufficient to allow normal vegetative growth and spore outgrowth of both wild-type and ponA cells in a medium with 500 mM NaCl. These studies demonstrate that (i) while HMW PBPs possess largely redundant functions in rich medium, when divalent cations are limiting, PBP1 is required for cell growth and spore outgrowth; and (ii) high levels of NaCl induce cell lysis in media deficient in divalent cations during both vegetative growth and spore outgrowth.

scholarly journals Permeation and interaction of divalent cations in calcium channels of snail neurons.

1985 ◽  
Vol 85 (4) ◽  
pp. 491-518 ◽  
Author(s):  
L Byerly ◽  
P B Chase ◽  
J R Stimers
Keyword(s):  
Mole Fraction ◽  
Surface Potential ◽  
Divalent Cation ◽  
Lymnaea Stagnalis ◽  
Divalent Cations ◽  
Ca Channel ◽  
Ca Current ◽  
Channel Current ◽  
Gating Mechanism ◽  
Ca Channel Current

We have studied the current-carrying ability and blocking action of various divalent cations in the Ca channel of Lymnaea stagnalis neurons. Changing the concentration or species of the permeant divalent cation shifts the voltage dependence of activation of the Ca channel current in a manner that is consistent with the action of the divalent cation on an external surface potential. Increasing the concentration of the permeant cation from 1 to 30 mM produces a twofold increase in the maximum Ca current and a fourfold increase in the maximum Ba current; the maximum Ba current is twice the size of the maximum Ca current for 10 mM bulk concentration. Correcting for the changing surface potential seen by the gating mechanism, the current-concentration relation is almost linear for Ba2+, and shows only moderate saturation for Ca2+; also, Ca2+, Ba2+, and Sr2+ are found to pass through the channel almost equally well. These conclusions are obtained for either of two assumptions: that the mouth of the channel sees (a) all or (b) none of the surface potential seen by the gating mechanism. Cd2+ blocks Lymnaea and Helix Ca channels at concentrations 200 times smaller than those required for Co2+ or Ni2+. Ca2+ competes with Cd2+ for the blocking site; Ba2+ binds less strongly than Ca2+ to this site. Mixtures of Ca2+ and Ba2+ produce an anomalous mole fraction effect on the Ca channel current. After correction for the changing surface potential (using either assumption), the anomalous mole fraction effect is even more prominent, which suggests that Ba2+ blocks Ca current more than Ca2+ blocks Ba current.

Rap1b Association with the Platelet Cytoskeleton Occurs in the Absence of Glycoproteins IIb/IIIa

1998 ◽  
Vol 79 (04) ◽  
pp. 832-836 ◽  
Author(s):  
Thomas Fischer ◽  
Christina Duffy ◽  
Gilbert White
Keyword(s):  
Molecular Weight ◽  
Divalent Cation ◽  
Binding Proteins ◽  
Binding Protein ◽  
Platelet Membrane ◽  
Low Molecular Weight ◽  
Membrane Glycoproteins ◽  
Gtp Binding Protein ◽  
Gtp Binding Proteins ◽  
Gtp Binding

SummaryPlatelet membrane glycoproteins (GP) IIb/IIIa and rap1b, a 21 kDa GTP binding protein, associate with the triton-insoluble, activation-dependent platelet cytoskeleton with similar rates and divalent cation requirement. To examine the possibility that GPIIb/IIIa was required for rap1b association with the cytoskeleton, experiments were performed to determine if the two proteins were linked under various conditions. Chromatography of lysates from resting platelets on Sephacryl S-300 showed that GPIIb/IIIa and rap1b were well separated and distinct proteins. Immunoprecipitation of GPIIb/IIIa from lysates of resting platelets did not produce rap1b or other low molecular weight GTP binding proteins and immunoprecipitation of rap1b from lysates of resting platelets did not produce GPIIb/IIIa. Finally, rap1b was associated with the activation-dependent cytoskeleton of platelets from a patient with Glanzmann’s thrombasthenia who lacks surface expressed glycoproteins IIb and IIIa. Based on these findings, we conclude that no association between GPIIb/IIIa and rap1b is found in resting platelets and that rap1b association with the activation-dependent cytoskeleton is at least partly independent of GPIIb/IIIa.

Crystal Structure of the GTP-binding Protein Obg from Thermus thermophilus HB8

2004 ◽  
Vol 337 (3) ◽  
pp. 761-770 ◽  
Author(s):  
Mutsuko Kukimoto-Niino ◽  
Kazutaka Murayama ◽  
Mio Inoue ◽  
Takaho Terada ◽  
Jeremy R.H. Tame ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Binding Protein ◽  
Thermus Thermophilus ◽  
Gtp Binding Protein ◽  
Thermus Thermophilus Hb8 ◽  
Gtp Binding

On tungstates of divalent cations (III) – Pb5O2[WO6]

2020 ◽  
Vol 235 (8-9) ◽  
pp. 311-317
Author(s):  
Stephan G. Jantz ◽  
Florian Pielnhofer ◽  
Henning A. Höppe
Keyword(s):  
Crystal Structure ◽  
Thermal Analysis ◽  
Quantum Chemical ◽  
Density Functional ◽  
Divalent Cations ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
First Results ◽  
Electrostatic Calculations

Abstract${\text{Pb}}_{5}{\text{O}}_{2}\left[{\text{WO}}_{6}\right]$ was discovered as a frequently observed side phase during our investigation on lead tungstates. Its crystal structure was solved by single-crystal X-ray diffraction ($P{2}_{1}/n$, $a=7.4379\left(2\right)$ Å, $b=12.1115\left(4\right)$ Å, $c=10.6171\left(3\right)$ Å, $\beta =90.6847\left(8\right)$°, $Z=4$, ${R}_{\text{int}}=0.038$, ${R}_{1}=0.020$, $\omega {R}_{2}=0.029$, 4188 data, 128 param.) and is isotypic with ${\text{Pb}}_{5}{\text{O}}_{2}\left[{\text{Te}}_{6}\right]$. ${\text{Pb}}_{5}{\text{O}}_{2}\left[{\text{WO}}_{6}\right]$ comprises a layered structure built up by non-condensed [WO6]${}^{6-}$ octahedra and ${\left[{\text{O}}_{4}{\text{Pb}}_{10}\right]}^{12+}$ oligomers. The compound was characterised by spectroscopic measurements (Infrared (IR), Raman and Ultraviolet–visible (UV/Vis) spectra) as well as quantum chemical and electrostatic calculations (density functional theory (DFT), MAPLE) yielding a band gap of 2.9 eV fitting well with the optical one of 2.8 eV. An estimation of the refractive index based on the Gladstone-Dale relationship yielded $n\approx 2.31$. Furthermore first results of the thermal analysis are presented.

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