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Octavian Călinescu
Max Planck Society
12Publications
7H-index
126Citations
Publications 12
Newest
#1Miyer Patiño-Ruiz (MPG: Max Planck Society)H-Index: 2
#2Klaus Fendler (MPG: Max Planck Society)H-Index: 28
Last.Octavian Călinescu (MPG: Max Planck Society)H-Index: 7
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Bacterial NhaB Na+/H+ exchangers belonging to the Ion Transporter superfamily are poorly characterized in contrast to Na+/H+ exchangers of the Cation Proton Antiporter superfamily which have NhaA from Escherichia coli as a prominent member. For a more detailed understanding of the intricacies of the exchanger’s transport mechanism, mutational studies are essential. Therefore, we mutated two protonatable residues present in the putative transmembrane region of NhaB from Klebsiella pneumoniae (KpN...
#1Miyer Patiño-Ruiz (MPG: Max Planck Society)H-Index: 2
#2Manish Dwivedi (HUJI: Hebrew University of Jerusalem)H-Index: 3
Last.Klaus Fendler (MPG: Max Planck Society)H-Index: 28
view all 6 authors...
#1Miyer Patiño-Ruiz (MPG: Max Planck Society)H-Index: 2
#2Constanta Ganea (MPG: Max Planck Society)H-Index: 12
Last.Octavian Călinescu (MPG: Max Planck Society)H-Index: 7
view all 4 authors...
Na+/H+ exchange is essential for survival of all organisms, having a role in the regulation of the intracellular Na+ concentration, pH and cell volume. Furthermore, Na+/H+ exchangers were shown to be involved in the virulence of the bacterium Yersinia pestis, indicating they might be potential targets for novel antibiotic treatments. The model system for Na+/H+ exchangers is the NhaA transporter from Escherichia coli, EcNhaA. Therefore, the general transport mechanism of NhaA exchangers is curre...
#1Octavian Călinescu (MPG: Max Planck Society)H-Index: 7
#2Manish Dwivedi (HUJI: Hebrew University of Jerusalem)H-Index: 3
Last.Klaus Fendler (MPG: Max Planck Society)H-Index: 28
view all 5 authors...
Na+/H+ antiporters are located in the cytoplasmic and intracellular membranes and play crucial roles in regulating intracellular pH, Na+, and volume. The NhaA antiporter of Escherichia coli is the best studied member of the Na+/H+ exchanger family and a model system for all related Na+/H+ exchangers, including eukaryotic representatives. Several amino acid residues are important for the transport activity of NhaA, including Lys-300, a residue that has recently been proposed to carry one of the t...
#1Octavian Călinescu (MPG: Max Planck Society)H-Index: 7
#2Mark Linder (MPG: Max Planck Society)H-Index: 1
Last.Klaus Fendler (MPG: Max Planck Society)H-Index: 28
view all 6 authors...
Abstract Na+/H+ antiporters in the CPA1 branch of the cation proton antiporter family drive the electroneutral exchange of H+ against Na+ ions and ensure pH homeostasis in eukaryotic and prokaryotic organisms. Although their transport cycle is overall electroneutral, specific partial reactions are electrogenic. Here, we present an electrophysiological study of the PaNhaP Na+/H+ antiporter from Pyrococcus abyssi reconstituted into liposomes. Positive transient currents were recorded upon addition...
#1Octavian Călinescu (UB: University of Bucharest)H-Index: 7
#2Nicoleta Mirela Marin (UB: University of Bucharest)H-Index: 2
Last.Hassan Y. Aboul-EneinH-Index: 46
view all 8 authors...
Abstract The sulfate anion is a stable, oxidized form of sulfur that is an essential nutrient for plants and animals. Due to its stability, sulfate is part of a large number of natural minerals, the most common being gypsum (CaSO 4 ·2H 2 O), anhydrite (CaSO 4 ), baryte (BaSO 4 ) and celestine (SrSO 4 ). Sulfate is an important component of non-polluted waters and is part of the six major ions in surface waters (Na + , Ca 2+ , Mg 2+ , Cl − , HCO 3 − , SO 4 2− ). Depending on its concentration, in...
#1Octavian Călinescu (MPG: Max Planck Society)H-Index: 7
#2Eva Danner (MPG: Max Planck Society)H-Index: 1
Last.Klaus Fendler (MPG: Max Planck Society)H-Index: 28
view all 5 authors...
Bacteria have adapted their NhaA Na+/H+ exchangers responsible for salt homeostasis to their different habitats. We present an electrophysiological and kinetic analysis of NhaA from Helicobacter pylori and compare it to the previously investigated exchangers from Escherichia coli and Salmonella typhimurium. Properties of all three transporters are described by a simple model using a single binding site for H+ and Na+. We show that H. pylori NhaA only has a small acidic shift of its pH-dependent ...
#1Octavian Călinescu (MPG: Max Planck Society)H-Index: 7
#2C. Paulino (MPG: Max Planck Society)H-Index: 8
Last.Klaus Fendler (MPG: Max Planck Society)H-Index: 28
view all 4 authors...
Na+/H+ exchangers are essential for regulation of intracellular proton and sodium concentrations in all living organisms. We examined and experimentally verified a kinetic model for Na+/H+ exchangers, where a single binding site is alternatively occupied by Na+ or one or two H+ ions. The proposed transport mechanism inherently down-regulates Na+/H+ exchangers at extreme pH, preventing excessive cytoplasmic acidification or alkalinization. As an experimental test system we present the first elect...
#1Dudu Alkoby (HUJI: Hebrew University of Jerusalem)H-Index: 3
#2Abraham Rimon (HUJI: Hebrew University of Jerusalem)H-Index: 24
Last.Etana Padan (HUJI: Hebrew University of Jerusalem)H-Index: 54
view all 7 authors...
pH and Na+ homeostasis in all cells requires Na+/H+ antiporters. The crystal structure, obtained at pH 4, of NhaA, the main antiporter of Escherichia coli, has provided general insights into an antiporter mechanism and its unique pH regulation. Here, we describe a general method to select various NhaA mutants from a library of randomly mutagenized NhaA. The selected mutants, A167P and F267C are described in detail. Both mutants are expressed in Escherichia coli EP432 cells at 70–95% of the wild ...
#1Andre Bazzone (MPG: Max Planck Society)H-Index: 5
#2Wagner Steuer Costa (Goethe University Frankfurt)H-Index: 7
Last.Klaus Fendler (MPG: Max Planck Society)H-Index: 28
view all 6 authors...
The electrophysiological method we present is based on a solid supported membrane (SSM) composed of an octadecanethiol layer chemisorbed on a gold coated sensor chip and a phosphatidylcholine monolayer on top. This assembly is mounted into a cuvette system containing the reference electrode, a chlorinated silver wire. After adsorption of membrane fragments or proteoliposomes containing the membrane protein of interest, a fast solution exchange is used to induce the transport activity of the memb...
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