Structural insights into the activation mechanism of melibiose permease by sodium binding

Meritxell Granell, Xavier León, Gérard Leblanc, Esteve Padrós, Víctor A. Lórenz-Fonfría

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Resum

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.
Idioma originalEnglish
Pàgines (de-a)22078-22083
RevistaProceedings of the National Academy of Sciences of the United States of America
Volum107
DOIs
Estat de la publicacióPublicada - 21 de des. 2010

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