Lateral diffusion of M-13 coat protein in model membranes

Area of Science:

• Biophysics
• Membrane Biology
• Protein Dynamics

Background:

• The M-13 phage coat protein is a well-characterized model system for studying protein behavior in membranes.
• Understanding protein diffusion and distribution is crucial for elucidating membrane function.

Purpose of the Study:

• To investigate the lateral diffusion and distribution of a fluorescently labeled M-13 phage coat protein in model membranes.
• To compare protein diffusion rates with lipid probes and assess the effect of membrane phase and composition.

Main Methods:

• Reconstitution of a fluorescent M-13 phage coat protein derivative into dimyristoylphosphatidylcholine (DMPC) multilayers and giant liposomes.
• Measurement of lateral diffusion rates as a function of temperature using fluorescence techniques.
• Analysis of protein lateral distribution in fluid and solid membrane phases.

Main Results:

• The lateral diffusion rate of the labeled protein in the fluid phase was comparable to that of lipid probes.
• The protein exhibited a nonuniform lateral distribution in the solid phase of both multilayers and liposomes.
• Inclusion of cardiolipin (0.5 mol %) did not substantially affect the protein's diffusion rate.

Conclusions:

• M-13 phage coat protein exhibits lipid-like diffusion in fluid lipid bilayers.
• Protein-lipid interactions lead to non-uniform distribution in solid membrane phases.
• Cardiolipin does not significantly alter the lateral mobility of M-13 phage coat protein in these model systems.