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 two H+ ions that NhaA exchanges for one Na+ ion during one transport cycle. Here, we sought to characterize the effects of mutating Lys-300 of NhaA to amino acid residues containing side chains of different polarity and length (i.e. Ala, Arg, Cys, His, Glu, and Leu) on transporter stability and function. Salt resistance assays, acridine-orange fluorescence dequenching, solid supported membrane-based electrophysiology, and differential scanning fluorometry were used to characterize Na+ and H+ transport, charge translocation, and thermal stability of the different variants. These studies revealed that NhaA could still perform electrogenic Na+/H+ exchange even in the absence of a protonatable residue at the Lys-300 position. However, all mutants displayed lower thermal stability and reduced ion transport activity compared with the wild-type enzyme, indicating the critical importance of Lys-300 for optimal NhaA structural stability and function. On the basis of these experimental data, we propose a tentative mechanism integrating the functional and structural role of Lys-300.
from #AlexandrosSfakianakis via Alexandros G.Sfakianakis on Inoreader http://ift.tt/2q8bypK
via IFTTT
Εγγραφή σε:
Σχόλια ανάρτησης (Atom)
Δημοφιλείς αναρτήσεις
-
Résumé L'extrait hydrométhanolique des parties aériennes d' Origanum glandulosum Batt. et Trab. a été étudié pour sa composition ...
-
Abstract Ethylene-octene copolymer (EOC)/organoclay nanocomposite was cured by peroxide in an internal mixer for different time periods. L...
-
http://ift.tt/2qKmhUL
-
Abstract Understanding the spatial distribution of PM 2.5 concentration and its contributing environmental variables is critical to devel...
-
Kinematic, Kinetic and Surface Electromyography Analysis Following Zygomatic Fracture ReconstructionAbstract The surgical indications of zygomatic fracture include aesthetic and functional impairment. No standard method exists for assessi...
-
Abstract The molecular genetic modifications in multiple genes involved in folate and homocysteine metabolism play the pivotal role in the...
-
Respiratory Polysomnographic Findings in Patients Treated Primarily for Unilateral Cleft Lip and Palate. Cleft Palate Craniofac J. 201...
-
Abstract AFLP analysis of 144 samples of tetraploid wheat species, including cultivars and landraces of Triticum durum from Azerbaijan, w...
-
Abstract The purpose of this study was to determine the different kinds and concentrations of intermediates, and investigate on the effect...
Δεν υπάρχουν σχόλια:
Δημοσίευση σχολίου