High affinity cation-binding sites in Complex I from Escherichia coli

Studies on the activity of Complex I from Escherichia coli in the presence of different metal cations revealed at least two high affinity metal-binding sites. Membrane-bound or isolated Complex I was activated by K(+) (apparent binding constant similar to 125 mu M) and inhibited by La(3+) (IC(50) = 1 mu M). K(+) and La(3+) do not occupy the same site. Possible localization of these metal-binding sites and their implication in catalysis are discussed. (C) 2009 Elsevier B.V. All rights reserved.