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Updated: Mar 24, 2026

Pull-down of Calmodulin-binding Proteins
Published on: January 23, 2012
Ca-Dependent Folding of Human Calumenin
Marco Mazzorana1, Rohanah Hussain1, Thomas Sorensen1
1Diamond Light Source, Ltd, Life Sciences Division, Harwell Science and Innovation Campus, Didcot, United Kingdom.
Human calumenin (hCALU) undergoes a structural transformation upon calcium binding, transitioning from a disordered to a compact, alpha-helical state. This calcium sensor folds into a functional conformation at millimolar calcium levels in the endoplasmic reticulum.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Human calumenin (hCALU) is a CREC family protein found in the secretory pathway.
- hCALU regulates SERCA2a and ryanodine receptor activity in the endoplasmic reticulum (ER).
Purpose of the Study:
- To investigate the structural changes in hCALU upon calcium (Ca2+) binding.
- To understand the functional implications of hCALU's structural transitions.
Main Methods:
- Circular Dichroism (CD) spectroscopy to analyze secondary structure changes.
- Small-Angle X-ray Scattering (SAXS) to determine overall protein structure.
- Investigated Ca2+ binding effects on protein conformation.
Main Results:
- Ca2+ binding induces a significant structural rearrangement in hCALU.
- CD measurements show a switch from disordered to alpha-helical structure with Ca2+ addition.
- SAXS data confirms a transition from an unfolded to a compact, trilobal fold.
Conclusions:
- hCALU functions as a Ca2+ sensor, undergoing a conformational change upon Ca2+ binding.
- The folded, compact structure is formed at millimolar Ca2+ concentrations in the ER.
- This Ca2+-induced folding enables interaction with molecular partners.
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