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Calcium Binding Mechanism in TAT Rhodopsin.
Teppei Sugimoto1, Koichi Miyagawa2, Mitsuo Shoji2
1Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.
The Journal of Physical Chemistry. B
|July 16, 2024
Summary
TAT rhodopsin binds calcium ions (Ca2+) near the Schiff base, causing its deprotonation. Molecular dynamics simulations reveal Ca2+ coordination and the crucial role of specific residues in this binding mechanism.
Area of Science:
- Structural biology
- Biophysics
- Computational chemistry
Background:
- TAT rhodopsin is a membrane protein involved in various cellular processes.
- Understanding the mechanism of cation binding is crucial for elucidating its function.
Purpose of the Study:
- To determine the Ca2+-free and Ca2+-bound structures of TAT rhodopsin.
- To elucidate the molecular mechanism of Ca2+ binding to TAT rhodopsin.
Main Methods:
- Molecular dynamics (MD) simulations initiated from AlphaFold structures.
- Fourier-transform infrared (FTIR) spectroscopy.
- Site-directed mutagenesis.
Main Results:
- Ca2+ is coordinated by eight oxygen atoms, including side chains of E54 and D227, and water molecules.
- Flipping motion of E54 facilitates Ca2+ binding and helix deformation.
- Mutations in key residues (E54, Y55, R79, Y200, E220, D227) abolish Ca2+ binding, except for T82V.
Conclusions:
- The study provides atomic-level insights into the Ca2+ binding mechanism of TAT rhodopsin.
- Specific amino acid residues and their interactions are critical for Ca2+ coordination and protein function.
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