Gramicidin A crystals contain two cation binding sites per channel

Nature ◽  
1979 ◽  
Vol 279 (5715) ◽  
pp. 723-725 ◽  
Author(s):  
ROGER E. KOEPPE ◽  
JEREMY M. BERG ◽  
KEITH O. HODGSON ◽  
LUBERT STRYER
Keyword(s):  
Binding Sites ◽  
Cation Binding ◽  
Gramicidin A

The divalent cation-binding sites of gramicidin A transmembrane ion-channel

Biopolymers ◽  
1991 ◽  
Vol 31 (4) ◽  
pp. 425-434 ◽  
Author(s):  
A. P. Golovanov ◽  
I. L. Barsukov ◽  
A. S. Arseniev ◽  
V. F. Bystrov ◽  
S. V. Sukhanov ◽  
...  
Keyword(s):  
Ion Channel ◽  
Divalent Cation ◽  
Binding Sites ◽  
Cation Binding ◽  
Gramicidin A

scholarly journals First Characterization of an Archaeal GTP-Dependent Phosphoenolpyruvate Carboxykinase from the Hyperthermophilic Archaeon Thermococcus kodakaraensis KOD1

2004 ◽  
Vol 186 (14) ◽  
pp. 4620-4627 ◽  
Author(s):  
Wakao Fukuda ◽  
Toshiaki Fukui ◽  
Haruyuki Atomi ◽  
Tadayuki Imanaka
Keyword(s):  
Binding Sites ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Cation Binding ◽  
Activity Levels ◽  
Binding Region ◽  
Hyperthermophilic Archaeon ◽  
Dependent Activity ◽  
Additional Role

ABSTRACT Phosphoenolpyruvate carboxykinase (PCK), which catalyzes the nucleotide-dependent, reversible decarboxylation of oxaloacetate to yield phosphoenolpyruvate and CO2, is one of the important enzymes in the interconversion between C3 and C4 metabolites. This study focused on the first characterization of the enzymatic properties and expression profile of an archaeal PCK from the hyperthermophilic archaeon Thermococcus kodakaraensis (Pck Tk ). Pck Tk showed 30 to 35% identities to GTP-dependent PCKs from mammals and bacteria but was located in a branch distinct from that of the classical enzymes in the phylogenetic tree, together with other archaeal homologs from Pyrococcus and Sulfolobus spp. Several catalytically important regions and residues, found in all known PCKs irrespective of their nucleotide specificities, were conserved in Pck Tk . However, the predicted GTP-binding region was unique compared to those in other GTP-dependent PCKs. The recombinant Pck Tk actually exhibited GTP-dependent activity and was suggested to possess dual cation-binding sites specific for Mn2+ and Mg2+. The enzyme preferred phosphoenolpyruvate formation from oxaloacetate, since the Km value for oxaloacetate was much lower than that for phosphoenolpyruvate. The transcription and activity levels in T. kodakaraensis were higher under gluconeogenic conditions than under glycolytic conditions. These results agreed with the role of Pck Tk in providing phosphoenolpyruvate from oxaloacetate as the first step of gluconeogenesis in this hyperthermophilic archaeon. Additionally, under gluconeogenic conditions, we observed higher expression levels of Pck Tk on pyruvate than on amino acids, implying that it plays an additional role in the recycling of excess phosphoenolpyruvate produced from pyruvate, replacing the function of the anaplerotic phosphoenolpyruvate carboxylase that is missing from this archaeon.

Furosemide-sensitive thallium fluxes in smooth muscle of rabbit uterus

1983 ◽  
Vol 245 (6) ◽  
pp. F778-F783
Author(s):  
A. Johns ◽  
S. V. Cutshaw
Keyword(s):  
Smooth Muscle ◽  
Binding Sites ◽  
Rank Order ◽  
Chloride Concentration ◽  
Cation Binding ◽  
Exchange System ◽  
Total Uptake ◽  
Low Concentrations ◽  
Chloride Pump ◽  
High Concentrations

The furosemide-sensitive uptake of thallium represents approximately equal to 50% of the total uptake of thallium by rabbit uterus and requires Cl- and Na+. The furosemide-sensitive uptake of thallium is stimulated by other ions at low concentrations with the rank order Li+ greater than Tl+ greater than K+ = Rb+ greater than Cs+ and is inhibited by these ions at high concentrations with the rank order Tl+ greater than K+ = Rb+ greater than Cs+ greater than Li+, suggesting multiple cation binding sites on the carrier. Uptake of 36Cl- is inhibited by furosemide in the presence of ouabain. Thallium efflux and 36Cl efflux in the presence of ouabain is inhibited by furosemide. The chloride concentration regulates the proportion of thallium uptake that is ouabain sensitive and furosemide sensitive without altering the total uptake. It is suggested that the furosemide-sensitive uptake of thallium reflects a Na+-Cl- -K+ exchange system that could be classified as a cotransport or countertransport of any two of these ions and also could be the smooth muscle chloride pump.

Inhibition of Aspergillus flavus and Selected Gram-positive Bacteria by Chelation of Essential Metal Cations by Polyphosphates

1991 ◽  
Vol 54 (5) ◽  
pp. 360-365 ◽  
Author(s):  
S.J. KNABEL ◽  
H.W. WALKER ◽  
P.A. HARTMAN
Keyword(s):  
Aspergillus Flavus ◽  
Binding Sites ◽  
Iron Supplementation ◽  
Cation Binding ◽  
Gram Negative Bacteria ◽  
Positive Bacterium ◽  
Gram Positive ◽  
Tetrasodium Pyrophosphate ◽  
Gram Positive Bacteria ◽  
And Staphylococcus Aureus

A simple well-plate technique was utilized to determine the effect of various metals on the growth of microorganisms in media containing different polyphosphates. Aspergillus flavus and four gram-positive bacteria were completely inhibited by media containing 1% of various alkaline polyphosphates, whereas four gram-negative bacteria were not. Significant differences were observed between the type of polyphosphate added, the type of metal added, and the species of gram-positive bacterium inhibited. The addition of Mg2+ stimulated growth of A. flavus and Bacillus cereus in the presence of tetrasodium pyrophosphate, whereas Mn2+ permitted growth of A. flavus and Staphylococcus aureus in the presence of sodium hexametaphosphate. Iron supplementation allowed the growth of S. aureus and Listeria monocytogenes on media containing 1 % tetrasodium pyrophosphate. A method for determining the amount of calcium and magnesium in water was modified to detect free Mg2+ by replacing EDTA with phosphate. The addition of free Mg2+, but not Mg2+ chelated by tetrasodium pyrophosphate, permitted the growth of B. cereus on a medium containing tetrasodium pyrophosphate. It is speculated that polyphosphates specifically inhibited A. flavus and gram-positive bacteria by removing essential metals from cation-binding sites located within their cell walls.

scholarly journals Probing ligand and cation binding sites in G-quadruplex nucleic acids by mass spectrometry and electron photodetachment dissociation sequencing

The Analyst ◽  
2019 ◽  
Vol 144 (11) ◽  
pp. 3518-3524 ◽  
Author(s):  
Dababrata Paul ◽  
Adrien Marchand ◽  
Daniela Verga ◽  
Marie-Paule Teulade-Fichou ◽  
Sophie Bombard ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Tandem Mass Spectrometry ◽  
Ligand Binding ◽  
Binding Sites ◽  
Cation Binding ◽  
Tandem Mass ◽  
Top Down ◽  
G Quadruplex ◽  
Ligand Binding Sites ◽  
Electron Photodetachment

Tandem mass spectrometry: native top-down sequencing by electron photodetachment dissociation (EPD) reveals ligand binding sites on DNA G-quadruplexes.

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