Figure 1.

Modelling SUR1. (A) The transmembrane topology of the sulphonylurea receptor SUR1, showing the transmembrane domains (TMDs) and the nucleotide-binding domains (NBDs). (B) Multiple sequence alignment used to generate the homology model, generated using ClustalW. Green shading indicates sequence homology and blue indicates sequence identity. Walker A (W_A), Walker B (W_B) and linker motifs are indicated. The asterisks indicate the conserved glutamine (in the Q-loop) and histidine (H-loop) residues. (C) Model of the NBDs of SUR1, showing the nucleotide-sandwich dimer and the conserved motifs. The W_A, W_B motifs and signature sequence are yellow, orange and green, respectively. NBD1 is blue and NBD2 is purple. Site 1 and site 2 are indicated. The SUR1 sequence was aligned with that of MJ0796 using ClustalW (Thompson, 1994) and the model generated using MODELLER 6v2 (Sali & Blundell, 1993) with the MJ0796 dimer crystal structure (PBD code 1L2T; Smith et al., 2002) input as the template. The MgATP molecule (shown in red) was added to each SUR model by least-squares fitting to the backbone atoms in the W_A motif of MJ0796. The Na-ATP coordinates were extracted from the MJ0796 PDB and Mg²⁺ was assumed to occupy the same position as Na⁺.