PUBLICATION
Physiologically Relevant Free Ca2+ Ion Concentrations Regulate STRA6-Calmodulin Complex Formation via the BP2 Region of STRA6
- Authors
- Young, B.D., Varney, K.M., Wilder, P.T., Costabile, B.K., Pozharski, E., Cook, M.E., Godoy-Ruiz, R., Clarke, O.B., Mancia, F., Weber, D.J.
- ID
- ZDB-PUB-211216-2
- Date
- 2021
- Source
- Journal of molecular biology 433: 167272 (Journal)
- Registered Authors
- Keywords
- STRA6, calmodulin, retinol, retinol-binding protein, vitamin A receptor
- MeSH Terms
-
- Calcium/metabolism*
- Vitamin A/metabolism
- EF Hand Motifs
- Spectrometry, Fluorescence
- Humans
- Membrane Transport Proteins/chemistry*
- Membrane Transport Proteins/genetics
- Membrane Transport Proteins/metabolism*
- Calmodulin/chemistry
- Calmodulin/genetics
- Calmodulin/metabolism*
- Protein Conformation
- Thermodynamics
- Zebrafish Proteins/chemistry*
- Zebrafish Proteins/genetics
- Zebrafish Proteins/metabolism*
- Peptide Fragments/chemistry
- Peptide Fragments/metabolism
- Multiprotein Complexes/metabolism
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Magnetic Resonance Spectroscopy
- PubMed
- 34592217 Full text @ J. Mol. Biol.
Citation
Young, B.D., Varney, K.M., Wilder, P.T., Costabile, B.K., Pozharski, E., Cook, M.E., Godoy-Ruiz, R., Clarke, O.B., Mancia, F., Weber, D.J. (2021) Physiologically Relevant Free Ca2+ Ion Concentrations Regulate STRA6-Calmodulin Complex Formation via the BP2 Region of STRA6. Journal of molecular biology. 433:167272.
Abstract
The interaction of calmodulin (CaM) with the receptor for retinol uptake, STRA6, involves an α-helix termed BP2 that is located on the intracellular side of this homodimeric transporter (Chen et al., 2016 [1]). In the absence of Ca2+, NMR data showed that a peptide derived from BP2 bound 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 EF-hand Ca2+-binding domains, EF3 and EF4 (CaKD = 60 ± 7 nM). As higher concentrations of free Ca2+ were achieved, CSPs occurred for residues in the N-terminal lobe (N-lobe) including those in EF1 and EF2 (CaKD = 1000 ± 160 nM). Thermodynamic and kinetic Ca2+ binding studies showed that BP2 addition increased the Ca2+-binding affinity of CaM and slowed its Ca2+ dissociation rates (koff) in both the C- and N-lobe EF-hand domains, respectively. These data are consistent with BP2 binding to the C-lobe of CaM at low free Ca2+ concentrations (<100 nM) like those found at resting intracellular levels. As free Ca2+ levels approach 1000 nM, which is typical inside a cell upon an intracellular Ca2+-signaling event, BP2 is shown here to interact with both the N- and C-lobes of Ca2+-loaded CaM (CaCaM-BP2). Because this structural rearrangement observed for the CaCaM-BP2 complex occurs as intracellular free Ca2+ concentrations approach those typical of a Ca2+-signaling event (CaKD = 1000 ± 160 nM), this conformational change could be relevant to vitamin A transport by full-length CaCaM-STRA6.
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