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Residue-residue interactions regulating the Ca2+-induced EF-hand conformation changes in calmodulin
Hiromitsu Shimoyama1, Mayuko Takeda-Shitaka1
1School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
Journal of Biochemistry
|April 4, 2017
Summary
Calcium binding to calmodulin (CaM) triggers conformational changes in its EF-hand motifs. Molecular dynamics simulations reveal key hydrophobic and hydrophilic residues involved in these Ca2+-induced structural transitions.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Calmodulin (CaM) is a crucial Ca2+-binding messenger protein.
- CaM contains four EF-hand motifs that undergo conformational changes upon Ca2+ binding.
Purpose of the Study:
- To investigate the mechanism by which Ca2+ binding induces conformational changes in CaM's EF-hand motifs.
- To identify specific residues involved in these Ca2+-dependent structural rearrangements.
Main Methods:
- Performed two 1μs molecular dynamics (MD) simulations of apo- and holo-CaM.
- Compared structures and interactions between apo- and holo-CaM simulations.
Main Results:
- Ca2+ binding weakens helix-helix interactions in all EF-hand motifs, promoting a closed-like conformation in holo-CaM.
- Identified key hydrophobic and hydrophilic residues (T34, H107, N111, Q143) mediating the open-to-close conformational changes.
- Observed similar interaction patterns in EF-hand 3 and 4, distinct from EF-hand 2, suggesting a unique regulatory role for EF-hand 2's polar residues.
Conclusions:
- Ca2+ binding induces significant conformational changes in CaM, driven by specific residue interactions.
- Hydrophilic residues play a critical role in stabilizing the EF-hand conformations.
- EF-hand 2 exhibits unique structural dynamics regulated by its polar residues.