Allosteric regulation of a prokaryotic small Ras-like GTPase contributes to cell polarity oscillations in bacterial motility
Fig 7
Ct-helix regulates MxMglAB interaction by binding to an allosteric pocket of the small Ras-like GTPase fold.
(A) A schematic representation of the conditions that facilitate MxMglAB complex formation. PDB IDs 6IZW, 3T12, and 5YMX correspond to the crystal structures of MxMglAB–GTPγS, TtMglAB–GTPγS, and MxMglA–GDP complexes. (B) Proposed model for MxMglAB relocalization. Proteins that can bind in the allosteric pocket potentially compete out the MxMglB Ct-helix and dissociate the MxMglAB–GDP complex. In panels A and B, MxMglB dimer is shown in magenta, whereas MxMglA conformations with the flipped and unflipped states of β2 are shown in green and brown, respectively. A 6-pointed yellow star and a 5-pointed light brown star represent GTP (labeled as “T”) and GDP (labeled as “D”), respectively. The β2 strand is represented by an arrow. The residues that form the interface are schematically shown by 2 circles on bottom or top of the β2 strand representation in the flipped and unflipped states of the strand, respectively. Ct-helix of MxMglB is schematically shown by a cylinder and labeled as “H.” Ct-helix, C-terminal helix; MxMglA–GDP, MxMglA bound to guanosine 5’-diphosphate; MxMglA, M. xanthus MglA; MxMglAB, M. xanthus MglA and MglB complex; MglAB–GTPγS, MglA and MglB complex formed in the presence of guanosine 5’-O-[gamma-thio]triphosphate; PDB ID, Protein Data Bank identification.