Calcium regulation of the human mitochondrial ATP-Mg/Pi carrier SLC25A24 uses a locking pin mechanism.

ABSTRACT: Mitochondrial ATP-Mg/Pi carriers import adenine nucleotides into the mitochondrial matrix and export phosphate to the cytosol. They are calcium-regulated to control the size of the matrix adenine nucleotide pool in response to cellular energetic demands. They consist of three domains: an N-terminal regulatory domain containing four calcium-binding EF-hands, a linker loop domain with an amphipathic ?-helix and a C-terminal mitochondrial carrier domain for the transport of substrates. Here, we use thermostability assays to demonstrate that the carrier is regulated by calcium via a locking pin mechanism involving the amphipathic ?-helix. When calcium levels in the intermembrane space are high, the N-terminus of the amphipathic ?-helix is bound to a cleft in the regulatory domain, leading to substrate transport by the carrier domain. When calcium levels drop, the cleft closes, and the amphipathic ?-helix is released to bind to the carrier domain via its C-terminus, locking the carrier in an inhibited state.

SUBMITTER: Harborne SP 

PROVIDER: S-EPMC5369052 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature