Essential Role of Cooperative Swing of Loops in the Transport Function of Mitochondrial ADP/ATP Carrier

Abstract

The mitochondrial ADP/ATP carrier, which mediates transport of ADP and ATP via the inner membrane, functions as a dimer, each subunit being located in the same orientation. The carrier has three large loops (M1, M2, M3) facing the matrix side. M1 loop is suggested to function as an outer gate, M2 as a substrate binding site and M3 as an auxiliary gate by interacting with other loops. The transport function of the carrier is characterized largely by the cooperative swing of these paired loops, in which location of loops changes repeatedly between outside and inside of the membrane.