Biophysical Characterization of Genetically Encoded Voltage Sensor ASAP1: Dynamic Range Improvement.

Area of Science:

• Biophysics
• Neuroscience
• Molecular Biology

Background:

• A novel fluorescent voltage sensor, ASAP1, has been developed for monitoring neuronal action potentials.
• ASAP1 is derived from Gallus gallus voltage-sensitive phosphatase with a modified GFP insertion.
• Crucial biophysical characteristics of ASAP1 require detailed investigation.

Purpose of the Study:

• To elucidate the biophysical properties of the ASAP1 voltage sensor.
• To correlate fluorescence signals with gating charge movement in ASAP1.
• To understand the kinetics of ASAP1 in response to voltage changes.

Main Methods:

• Utilized the cut-open voltage clamp technique in Xenopus laevis oocytes expressing ASAP1.
• Simultaneously recorded fluorescence signals and gating currents.
• Analyzed the relationship between charge movement and fluorescence kinetics.

Main Results:

• ASAP1 fluorescence signals closely track gating charge movement.
• ASAP1 exhibits significantly faster gating currents compared to Ciona intestinalis voltage-sensitive phosphatase.
• Modification of a specific residue resolved a split in the ASAP1 Q-V curve while maintaining accelerated kinetics.

Conclusions:

• ASAP1 demonstrates rapid gating kinetics suitable for tracking action potentials.
• The biophysical characterization provides a foundation for optimizing voltage sensor design.
• ASAP1 is a promising tool for high-resolution optical monitoring of neuronal activity.