Dynamics of myo1c (myosin-ibeta ) lipid binding and dissociation

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Myosin-I is a single-headed myosin that interacts with lipid membranes.
• Membrane binding is attributed to electrostatic forces between the myosin-I tail and acidic phospholipids.

Purpose of the Study:

• To investigate the dynamics of myosin-I membrane association using a recombinant myo1c tail domain.
• To quantify the rates of association and dissociation of myo1c tail to lipid membranes.

Main Methods:

• Utilized fluorescence resonance energy transfer (FRET) to measure binding kinetics.
• Employed large unilamellar vesicles (LUVs) as model membranes.
• Investigated the effect of calcium ions and phospholipid concentration on binding rates.

Main Results:

• Lipid-tail association rate is fast in the absence of calcium, approaching diffusion-limited binding.
• Calcium ions decrease the association rate of myo1c tail to membranes.
• Dissociation kinetics exhibit two components: a calcium-dependent fast phase and a slower phase dependent on acidic phospholipid ratio.
• The slow dissociation component rate is slower than the myosin-I ATPase rate, indicating sustained membrane interaction.

Conclusions:

• Myosin-I exhibits rapid electrostatic membrane association, modulated by calcium.
• Calcium prolongs myosin-I membrane residence time, potentially impacting its function during multiple catalytic cycles.
• Understanding these dynamics is crucial for elucidating myosin-I's role in cellular processes involving membrane interactions.