Dimeric arrangement, flexibility and intermolecular contacts in wild-type GLTP (wtGLTP) and the D48V mutant complexed with the short-acyl-chain sulfatide 12:0 monoSF. (a, b) Open dimer conformation in wtGLTP (a) versus the locked dimer of D48V (b). Protein chains are coloured blue for wtGLTP and gold for the D48V mutant. Sulfatide atoms are coloured red, blue and green for oxygen, nitrogen and sulfur, respectively, while C atoms are coloured pink for the lipid bound to wtGLTP and blue for the lipid bound to the D48V mutant. The eight α-helices of the GLTP fold are labelled α1–α8. The values 80° and 65° indicate the mutual inclination of two α2 helices in the dimeric structure of wtGLTP versus D48V-GLTP. (c) Comparative superimposition of `open' and `closed' dimer conformations for different wtGLTP crystal forms (referred to as WT3 and WT2). Protein Cα chains are coloured blue and green for different dimers. The monomers on the left are superimposed to highlight the range of openness of the monomer on the right for the different dimers. Blue and green semi-transparent solid shapes additionally highlight the superimposition of the left monomers and the range of openness of the right monomer for the different dimers. Ligand molecules are omitted for clarity. (d) Schematic highlighting the closed and locked conformation of the D48V dimers. Complexes with 12:0 monoSF and with 12:0-diSF are shown by solid shapes coloured yellow and red–brown, respectively, with α2, α6 and α8 indicating selected helices and the rectangle denoting the hydrophobic core that `locks' the dimer. For the superposition of Cα chains, see Supplementary Fig. S1(c). (e–g) Protein–protein′ dimeric contact regions shown by comparative superimposition of wtGLTP and D48V: overall view (e) and two zones of expanded contacts in the locked dimer (f, g). Superpositioning details and colour codes are as in (a) and (c). Wide dashed bands show expanded contacts. Solid straight lines are conditional axes of α2 helices, while dashed lines with values indicate the midpoint distances between them (t distances in Table 3).