Calcium-dependent structural changes in human reticulocalbin-1
Nanao Suzuki1, Syoko Ban, Eriko Itoh
1Department of Chemistry, Graduate School of Science, Chiba University, Chiba 263-8522, Japan; Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan; and Laboratory of Chemistry, College of Liberal and Sciences, Tokyo Medical and Dental University, Chiba 272-0827, Japan.
Insights
Human reticulocalbin-1 (hRCN1), a calcium-binding protein, undergoes structural changes upon Ca(2+) binding. This calcium-induced conformational shift in the CREC family may regulate protein interactions within the secretory pathway.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Human reticulocalbin-1 (hRCN1) is a Ca(2+)-binding protein within the CREC family, localized to the secretory pathway.
- The precise cellular function of hRCN1 remains largely undetermined.
Purpose of the Study:
- To investigate the structural and functional properties of hRCN1.
- To elucidate the effects of Ca(2+) binding on hRCN1 conformation and its implications for protein function.
Main Methods:
- Developed a novel bacterial expression and purification protocol for recombinant hRCN1.
- Utilized biophysical techniques including gel-filtration chromatography and small-angle X-ray scattering.
- Assessed Ca(2+) and Mg(2+) binding effects on protein structure and conformation.
Main Results:
- Established an efficient method for hRCN1 production and purification.
- Demonstrated cooperative Ca(2+) binding to hRCN1, leading to increased α-helix content.
- Observed no significant structural changes upon Mg(2+) binding.
- Showed Ca(2+) binding induces a more compact monomeric structure in hRCN1.
- Reported the first evidence of Ca(2+)-dependent conformational changes within the CREC protein family.
Conclusions:
- hRCN1 undergoes significant conformational alterations in response to Ca(2+) binding.
- These Ca(2+)-induced structural changes are specific and do not occur with Mg(2+).
- The findings suggest a mechanism where Ca(2+) binding regulates the interactions of CREC family proteins within the secretory pathway.
Abstract:
Human reticulocalbin-1 (hRCN1) has six EF-hand motifs and binds Ca(2+). hRCN1 is a member of the CREC family localized in the secretory pathway, and its cellular function remains unclear. In this study, we established a new bacterial expression and purification procedure for hRCN1. We observed that hRCN1 binds Ca(2+) in a cooperative manner and the Ca(2+) binding caused an increase in the α-helix content of hRCN1. On the other hand, hRCN1 did not change the structure with Mg(2+) loading. hRCN1 is a monomeric protein, and its overall structure became more compact upon Ca(2+) binding, as revealed by gel-filtration column chromatography and small-angle X-ray scattering. This is the first report of conformational changes in the CREC family upon Ca(2+) binding. Our data suggest that CREC family member interactions with target proteins are regulated in the secretory pathway by conformational changes upon Ca(2+) binding.
More Related Videos
11:25Targeting Cysteine Thiols for in Vitro Site-specific Glycosylation of Recombinant Proteins
Published on: October 4, 2017
12:01Acute Dissociation of Lamprey Reticulospinal Axons to Enable Recording from the Release Face Membrane of Individual Functional Presynaptic Terminals
Published on: October 1, 2014
Related Concept Videos
01:33Overview of Secretory Vesicles
Various proteins regulate the aggregation of molecules inside the secretory vesicles. Chromogranins...
01:16Calmodulin-dependent Signaling
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
01:29Protein Folding Quality Check in the RER