Disulfatide binding to wtGLTP and the D48V mutant. (a) 3,6-O-Disulfo-Gal headgroup in the wtGLTP recognition centre. Dashed lines indicate hydrogen bonds. Disulfatide atoms are coloured red, blue, green and magenta for oxygen, nitrogen, sulfur and carbon, respectively. Protein Cα backbone and side-chain C atoms are coloured silver and gold, respectively. The grey circle labelled W1 or W indicates the conserved water molecule. S1 and S2 (pink rectangles) are 3-O- and 6-O-sulfo groups, respectively. (b) Chemical structure of N-lauroyl-3,6-O-disulfo-galactosylceramide. (c) 3,6-O-Disulfo-Gal headgroup in the recognition centre of the D48V mutant. Colour codes and designations are as in (a), except for ligand C atoms, which are coloured cyan. The mutated residue 48 is shown in a red circle; the black arrow points out the different conformation of S2 compared with that in wtGLTP (a). (d, e) Electrostatic surface view (blue, positive; red, negative; grey, neutral) of the GLTP recognition centre in the wild-type protein (d) and the D48V mutant (e) occupied by a disulfatide molecule shown in stick representation within a space-filled semitransparent shape with green-coloured sulfo groups. Colour codes are as in (a) and (b). The mutated residue is shown in a red circle; arrows point out the `empty' space (filled by water molecules) resulting from the D48V mutation and the conformational change of the S2 group promoting the movement of the C-end. (f, h) Dimeric arrangements of 12:0-diSF in wtGLTP (f) and D48V (h), with the ligand in ball-and-stick representation. Colour codes are as in Figs. 2(d) and (e). (g) Superimposed disulfatide molecules as bound to D48V (cyan) versus wtGLTP (magenta).