Photoreversible conductance changes induced by phytochrome in model lipid membranes

Area of Science:

• Biophysics
• Plant Molecular Biology
• Membrane Science

Background:

• Phytochrome is a plant photoreceptor crucial for light-dependent development.
• Black lipid membranes (BLMs) serve as model systems for cellular membranes.
• Understanding light-induced molecular changes in membranes is key to biophysical studies.

Purpose of the Study:

• To investigate the effect of plant phytochrome on the electrical properties of a model membrane.
• To determine if phytochrome's photoreversible activity can be observed in a non-biological system.
• To explore the potential of BLMs for studying light-sensitive proteins.

Main Methods:

• Incorporation of purified plant phytochrome into oxidized cholesterol black lipid membranes.
• Measurement of membrane conductance under controlled illumination conditions.
• Application of red light (approx. 660 nm) and far-red light (approx. 730 nm) to induce spectral transitions in phytochrome.
• Comparison of conductance changes with native and denatured phytochrome.

Main Results:

• Phytochrome induced significant, reversible changes in BLM conductance.
• Red light illumination led to an increase in membrane conductance.
• Far-red light illumination reversed the effect, decreasing membrane conductance.
• Denatured phytochrome did not elicit any changes in membrane conductance, confirming protein integrity is essential.

Conclusions:

• Plant phytochrome can modulate the electrical conductance of a lipid bilayer membrane in a light-dependent manner.
• This study demonstrates a direct biophysical effect of phytochrome's light-sensing mechanism outside of its native cellular environment.
• Oxidized cholesterol BLMs provide a viable platform for studying the photochemistry and biophysics of photoreceptor proteins like phytochrome.