  Protein function may be modulated by an event occurring far away from the
functional site, a phenomenon termed allostery. While classically allostery
involves conformational changes, we recently observed that charge
redistribution within an antibody can also lead to an allosteric effect,
modulating the kinetics of binding to target antigen. In the present study, we
study the association of a poly-histidine tagged enzyme (phosphoglycerate
kinase, PGK) to surface-immobilized anti-His antibodies, finding a significant
Charge-Reorganization Allostery (CRA) effect. We further observe that the
negatively charged nucleotide substrates of PGK modulate CRA substantially,
even though they bind far away from the His-tag-antibody interaction interface.
In particular, binding of ATP reduces CRA by more than 50%. The results
indicate that CRA may be affected by charged substrates bound to a protein and
provide further insight into the role of charge redistribution in protein
function.
