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Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

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Harnessing Environmental Ca²⁺ for Extracellular Protein Thermostabilization.

Malin J Allert¹, Homme W Hellinga¹

¹Department of Biochemistry, Duke University Medical Center, P.O. Box 3711, Durham, North Carolina 27710, United States.

|September 11, 2020

Summary

Calcium (Ca2+) binding to EF hands in extracellular proteins stabilizes them by altering protein structure. This conformational coupling mechanism is key for Ca2+-mediated thermostabilization and allosteric control.

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Area of Science:

Biochemistry
Structural Biology
Biophysics

Background:

Calcium (Ca2+) is abundant, and EF hand motifs bind it in proteins.
Intracellular EF hand proteins regulate signal transduction via Ca2+-induced conformational changes.
Extracellular Ca2+ binding's role in protein stability is less understood.

Purpose of the Study:

Investigate Ca2+ binding to extracellular EF hands.
Determine if Ca2+ binding confers thermostability.
Elucidate the conformational coupling mechanisms involved.

Main Methods:

Studied the extracellular glucose-galactose binding protein (ecGGBP) from E. coli.
Measured thermostability changes upon Ca2+ binding.
Utilized statistical thermodynamic analysis of a fluorescently labeled protein conjugate.

Main Results:

Ca2+ binding to ecGGBP's EF hand increased thermostability by ~17 K.
Conformational coupling mechanisms in two exchange reactions drive Ca2+-mediated stabilization.
A disorder-to-order transition in the folded state is crucial for Ca2+-bound state dominance.

Conclusions:

Extracellular Ca2+ binding stabilizes proteins through conformational coupling.
This mechanism is shared between thermostabilization and allosteric control in signal transduction.
Findings suggest evolutionary links between EF hand functions.