A self-sequestered calmodulin-like Ca²? sensor of mitochondrial SCaMC carrier and its implication to Ca²?-dependent ATP-Mg/P(i) transport.

ABSTRACT: The mitochondrial carriers play essential roles in energy metabolism. The short Ca²?-binding mitochondrial carrier (SCaMC) transports ATP-Mg in exchange for Pi and is important for activities that depend on adenine nucleotides. SCaMC adopts, in addition to the transmembrane domain (TMD) that transports solutes, an extramembrane N-terminal domain (NTD) that regulates solute transport in a Ca²?-dependent manner. Crystal structure of the Ca²?-bound NTD reveals a compact architecture in which the functional EF hands are sequestered by an endogenous helical segment. Nuclear magnetic resonance (NMR) relaxation rates indicated that removal of Ca²? from NTD results in a major conformational switch from the rigid and compact Ca²?-bound state to the dynamic and loose apo state. Finally, we showed using surface plasmon resonance and NMR titration experiments that free apo NTDs could specifically interact with liposome-incorporated TMD, but that Ca²? binding drastically weakened the interaction. Our results together provide a molecular explanation for Ca²?-dependent ATP-Mg flux in mitochondria.

SUBMITTER: Yang Q 

PROVIDER: S-EPMC3946054 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature