Subunit communication in the tryptophan synthase α2β2 complex Effects of β subunit ligands on proteolytic cleavage of a flexible loop in the α subunit

摘要

>To probe the structural basis for ligand-mediated communication between the α and β subunits in the tryptophan synthase α₂β₂ complex, we have determined the effects of ligands of the α and β subunits on proteolysis of a flexible loop in the α subunit. We find that addition of a ligand of the β subunit ( class="smallCaps">l-serine, class="smallCaps">d-tryptophan, or class="smallCaps">l-tryptophan) in combination with a ligand of the α subunit (α-glycerol 3-phosphate) almost completely prevents the tryptic cleavage of the α subunit loop. Thus, the binding of a ligand to the β-site affects the conformation of the α subunit 25–30 Å distant.