Structural dynamics of the magnesium-bound conformation of CorA in a lipid bilayer.
The transmembrane conformation of Thermotoga maritima CorA, a magnesium transport system, has been studied in its Mg(2+)-bound form by site-directed spin labeling and electron paramagnetic resonance spectroscopy. Probe mobility together with accessibility data were used to evaluate the overall dynamics and relative arrangement of individual transmembrane segments TM1 and TM2. TM1 extends toward the cytoplasmic side creating a water-filled cavity, while TM2 is located in the periphery of the oligomer, contacting the lipid bilayer. A structural model for the conserved extracellular loop was generated based on EPR data and MD simulations, in which residue E316 is located toward the five-fold symmetry axis in position to electrostatically influence divalent ion translocation. Electrostatic analysis of our model suggest that, in agreement with the crystal structure, Mg(2+) -bound CorA is in a closed conformation. The present results suggest that long-range structural rearrangements are necessary to allow Mg(2+) translocation.
Dalmas
Olivier
O
Department of Biochemistry and Molecular Biology, Institute for Biophysical Dynamics, The University of Chicago, IL 60637, USA.
Cuello
Luis G
LG
Jogini
Vishwanath
V
Cortes
D Marien
DM
Roux
Benoit
B
Perozo
Eduardo
E
D027682:Cation Transport Proteins / Q000737:chemistry*; D004492:Edetic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D008051:Lipid Bilayers / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry*; D008958:Models, Molecular; D010100:Oxygen / Q000378:metabolism; D011487:Protein Conformation; D013113:Spin Labels; D055672:Static Electricity; D020124:Thermotoga maritima / Q000737:chemistry*
D027682:Cation Transport Proteins; D008051:Lipid Bilayers; D013113:Spin Labels; C026058:EDDA; D004492:Edetic Acid; D008274:Magnesium; D010100:Oxygen