A Complex between the Catalytic and Regulatory Subunits of Aspartate Transcarbamylase

The effects of subunit interactions on the function of aspartate transcarbamylase from Escherichia coli have been studied by examining possible intermediates during the renaturation of the enzyme from the separated catalytic subunit (c3) and regulatory subunit (r2). When excess r2 is added to a very dilute solution of c3 (1.5 µg per ml or less), a complex is initially formed which, at pH 8.5, differs in kinetic properties from either c3 or the …