Calcium-induced conformational changes of the regulatory domain of human mitochondrial aspartate/glutamate carriers

Nat Commun. 2014 Nov 20:5:5491. doi: 10.1038/ncomms6491.

Abstract

The transport activity of human mitochondrial aspartate/glutamate carriers is central to the malate-aspartate shuttle, urea cycle, gluconeogenesis and myelin synthesis. They have a unique three-domain structure, comprising a calcium-regulated N-terminal domain with eight EF-hands, a mitochondrial carrier domain, and a C-terminal domain. Here we present the calcium-bound and calcium-free structures of the N- and C-terminal domains, elucidating the mechanism of calcium regulation. Unexpectedly, EF-hands 4-8 are involved in dimerization of the carrier and form a static unit, whereas EF-hands 1-3 form a calcium-responsive mobile unit. On calcium binding, an amphipathic helix of the C-terminal domain binds to the N-terminal domain, opening a vestibule. In the absence of calcium, the mobile unit closes the vestibule. Opening and closing of the vestibule might regulate access of substrates to the carrier domain, which is involved in their transport. These structures provide a framework for understanding cases of the mitochondrial disease citrin deficiency.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aspartic Acid / metabolism*
  • Calcium / metabolism*
  • Crystallography, X-Ray
  • Glutamic Acid / metabolism*
  • Humans
  • Mitochondria / metabolism*
  • Mitochondrial Membrane Transport Proteins / metabolism*
  • Protein Conformation
  • Protein Structure, Tertiary

Substances

  • Mitochondrial Membrane Transport Proteins
  • SLC25A12 protein, human
  • SLC25A13 protein, human
  • Aspartic Acid
  • Glutamic Acid
  • Calcium

Associated data

  • PDB/4P5W
  • PDB/4P5X
  • PDB/4P60