Fig. 3
From: The extracellular gate shapes the energy profile of an ABC exporter
Structural analysis of the closed NBD dimer. a The fully closed NBD dimer (NBD287 in teal and NBD288 in magenta) sandwiches two ATPγS-Mg molecules (shown as sticks with corresponding electron density) between Walker A motif (red) and the opposite ABC signature motif (green) at the degenerate and the consensus site in a highly symmetric manner. Residues involved in ATP binding and hydrolysis are shown as sticks. b Superimposition of the consensus ATP binding site of the previously solved IF structure (PDB: 4Q4A, light pink) and the OF structure (magenta). Distortions of the catalytic dyad (E517TM288 and H548TM288) are relaxed during NBD closure to adopt a hydrolysis-competent arrangement. The side chain of E517TM288 was modeled into the TM287/288(EtoA) structure. c Slice-cut through the two nucleotide binding sites reveals two possible Pi exit tunnels at the consensus site which are not present at the degenerate site. ATPγS (partially clipped) is shown as yellow sticks
