Fig. 6: Comparison of the regulatory elements between the tbNadE and hsNadE complexes.

a, b Cartoon structures of the closed P2 loop (cyan), the α-17 helix (purple), and the YRE loop (orange for the coupled subunit, and brown for the uncoupled subunit) in tbNadE–SFI complex bound to glutamine (a) and hsNadE (b). Panel a shows the α-17 helix connecting the closed P2 loop of B^syn to the YRE loop of the coupled subunit D^glu. This YRE loop makes also contact with the YRE loop of the uncoupled subunit ^symC thus resulting in a productive binding of the glutamine substrate in ^symC of tbNadE. Panel b shows the α17 connects the closed P2 and YRE loops with the same subunit (chain A) in hsNadE. The pairs of Arg128^TB/Arg576^TB and Glu120^HS/Lys609^HS connecting the YRE and α-17 helix of the coupled subunits in tbNadE and hsNadE, respectively, are shown as orange and purple spheres. The Tyr131^TB/^symCTyr131^TB in tbNadE are shown as orange and brown spheres, respectively. The catalytic cysteine and the C176A variant in the glutaminase active site are shown as yellow spheres. The Caver calculated ammonia and glutamine tunnels are shown in golden and gray, respectively.