PDBsum entry 4n5x

Calcium-binding protein

PDB id: 4n5x

Contents

Protein chain

155 a.a.

Ligands

PEG

Metals

_CA ×5

Waters ×124

References listed in PDB file

Key reference

• Title: A self-Sequestered calmodulin-Like ca²⁺ sensor of mitochondrial scamc carrier and its implication to ca²⁺-Dependent ATP-Mg/p(i) transport.
• Authors: Q.Yang, S.Brüschweiler, J.J.Chou.
• Ref.: Structure, 2014, 22, 209-217. [DOI no: 10.1016/j.str.2013.10.018]
• PubMed id: 24332718

Abstract

The mitochondrial carriers play essential roles in energy metabolism. The short Ca(2+)-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 Ca(2+)-dependent manner. Crystal structure of the Ca(2+)-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 Ca(2+) from NTD results in a major conformational switch from the rigid and compact Ca(2+)-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 Ca(2+) binding drastically weakened the interaction. Our results together provide a molecular explanation for Ca(2+)-dependent ATP-Mg flux in mitochondria.