Calmodulin-STRA6 complex formation is regulated by Ca2+

Abstract

Calmodulin (CaM) interacts with the receptor for retinol uptake, STRA6, at a helix termed BP2 which is located on the intracellular side of this homodimeric transmembrane receptor. NMR and biophysical studies were performed to determine the molecular mechanism by which CaM interacts with a peptide derived from zebrafish BP2. In the absence of Ca2+, BP2 was found to bind to the C-terminal lobe (C-lobe) of Mg2+-bound CaM (MgCaM). Upon titration of Ca2+ into MgCaM-BP2, NMR chemical shift perturbations (CSPs) were observed for residues in the C-lobe including those in the Ca2+-binding domains, EF-hands, EF3 and EF4 (CaKD = 60 ± 7 nM).