Identification of the E2-binding residues in the N-terminal domain of E1 of a prokaryotic pyruvate dehydrogenase complex.

Pyruvate dehydrogenase (E1p) is one of the components of the pyruvate dehydrogenase multienzyme complex (PDHC). Previously, it was shown that the N-terminal domain of E1p is involved in its binding to the core component (E2p) of PDHC. We constructed point mutations in this domain (D17Q, D17R, E20Q, E20R, D24Q and D24R) to identify the specific residues involved in these interactions. Kinetic and binding studies show that D17 is essential for the binding of E1p to E2p. D24 is involved in the binding, but not essential, whereas E20 is not involved. None of the mutations affects the folding or dimerisation of E1p.