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Optical switching of dipolar interactions on proteins
Tomoyo Sakata1, Yuling Yan, Gerard Marriott
1Department of Physiology, University of Wisconsin, 1300 University Avenue, Madison, WI 53705, USA.
Summary
Optical switching of photochromes on G-actin reversibly controls protein interactions. This light-induced modulation of spiro (SP) and merocyanine (MC) states offers precise control over biological functions.
Area of Science:
- Biochemistry
- Photochemistry
- Molecular Biology
Background:
- G-actin is a key protein in cellular processes.
- Photochromic molecules can switch between states upon light exposure.
- Modulating protein interactions is crucial for biological control.
Purpose of the Study:
- To investigate optical switching of photochromes on G-actin.
- To determine if this switching can modulate dipolar interactions.
- To explore potential applications in controlling protein function.
Main Methods:
- Selective labeling of G-actin with spirobenzopyran and spironaphthoxazine photochromes.
- Optical spectroscopy to study interactions between photochrome states and G-actin.
- Alternate light excitation (365 nm and 546 nm) to induce SP to MC and MC to SP state transitions.
Main Results:
- Optical switching between spiro (SP) and merocyanine (MC) states was achieved with high fidelity.
- The merocyanine (MC) state exhibited sensitivity to polar interactions, unlike the spiro (SP) state.
- A significant free energy difference (6 kcal/mol) was observed for dipolar interactions between MC states within G-actin.
Conclusions:
- Optical switching of photochromes on G-actin can rapidly and reversibly modulate specific dipolar interactions.
- The observed energy differences are comparable to those in G-actin regulatory protein complexes.
- This light-controlled mechanism could potentially inhibit functional interactions with ligands in the MC state.