The β-strand arrangement of the DC-LAMP domain. The 'front' and 'back' β-sheets are drawn in red and blue, respectively. The cysteines that form the first disulfide bond (S-S) are labelled. β-strands and loops are identified as S1 to S11 and L1 to L3, respectively. The topology of the β-sheets is drawn schematically in the lower part with sheets opened out.