Most
reported bacterial phosphofructokinases (Pfks) are tetramers
that exhibit activity allosterically regulated via conformational
changes between the R and T states. We report that the Pfk from <i>Staphylococcus aureus</i> NCTC 8325 (<i>Sa</i>Pfk)
exists as both an active tetramer and an inactive dimer in solution.
Multiple effectors, including pH, ADP, ATP, and adenylyl-imidodiphosphate
(AMP-PNP), cause equilibrium shifts from the tetramer to dimer, whereas
the substrate F6P stabilizes <i>Sa</i>Pfk tetrameric assembly.
Crystal structures of <i>Sa</i>Pfk in complex with different
ligands and biochemical analysis reveal that the flexibility of the
Gly150-Leu151 motif in helix α7 plays a role in tetramer–dimer
conversion. Thus, we propose a molecular mechanism for allosteric
regulation of bacterial Pfk via conversion between the tetramer and
dimer in addition to the well-characterized R-state/T-state mechanism
