TY - JOUR
T1 - Structural insights into the activation mechanism of melibiose permease by sodium binding
AU - Granell, Meritxell
AU - León, Xavier
AU - Leblanc, Gérard
AU - Padrós, Esteve
AU - Lórenz-Fonfría, Víctor A.
PY - 2010/12/21
Y1 - 2010/12/21
N2 - The melibiose carrier from Escherichia coli (MelB) couples the accumulation of the disaccharide melibiose to the downhill entry of H , Na+, orLi+. In this work, substrate-induced FTIR difference spectroscopy was used in combination with fluorescence spectroscopy to quantitatively compare the conformational properties of MelB mutants, implicated previously in sodium binding, with those of a fully functional Cys-less MelB permease. The results first suggest that Asp55 and Asp59 are essential ligands for Na binding. Secondly, though Asp124 is not essential for Na+ binding, this acidic residue may play a critical role, possibly by its interaction with the bound cation, in the full Na+ -induced conformational changes required for efficient coupling between the ion- and sugar-binding sites; this residue may also be a sugar ligand. Thirdly, Asp19 does not participate in Na+ binding but it is a melibiose ligand. The location of these residues in two independent threading models of MelB is consistent with their proposed role.
AB - The melibiose carrier from Escherichia coli (MelB) couples the accumulation of the disaccharide melibiose to the downhill entry of H , Na+, orLi+. In this work, substrate-induced FTIR difference spectroscopy was used in combination with fluorescence spectroscopy to quantitatively compare the conformational properties of MelB mutants, implicated previously in sodium binding, with those of a fully functional Cys-less MelB permease. The results first suggest that Asp55 and Asp59 are essential ligands for Na binding. Secondly, though Asp124 is not essential for Na+ binding, this acidic residue may play a critical role, possibly by its interaction with the bound cation, in the full Na+ -induced conformational changes required for efficient coupling between the ion- and sugar-binding sites; this residue may also be a sugar ligand. Thirdly, Asp19 does not participate in Na+ binding but it is a melibiose ligand. The location of these residues in two independent threading models of MelB is consistent with their proposed role.
KW - Infrared spectroscopy
KW - Ligand binding
KW - Membrane proteins
KW - Sugar/cation symporter
U2 - https://doi.org/10.1073/pnas.1008649107
DO - https://doi.org/10.1073/pnas.1008649107
M3 - Article
VL - 107
SP - 22078
EP - 22083
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
ER -