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Interaction of synapsin I with membranes
James J Cheetham1, Jill Murray, Marina Ruhkalova
1Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ont., Canada K1S 5B6. jcheetha@ccs.carleton.ca
Biochemical and Biophysical Research Communications
|September 19, 2003
Summary
Synapsin I protein binds strongly to liposomes, increasing their positive surface charge and causing aggregation without leakage. This suggests amphipathic protein regions mediate membrane interactions and stabilization.
Area of Science:
- Neuroscience
- Biochemistry
- Cell Biology
Background:
- Synapsins (I, II, III) are peripheral membrane proteins crucial for neurotransmitter release and synaptogenesis.
- They localize to presynaptic nerve terminals, associating with synaptic vesicles.
Purpose of the Study:
- To investigate the molecular mechanisms of synapsin I binding to membranes.
- To understand how synapsin I interacts with lipid components of synaptic vesicles.
Main Methods:
- Studied bovine synapsin I binding to liposomes using fluoresceinphosphatidyl-ethanolamine (FPE) to measure membrane electrostatic potential.
- Analyzed synapsin I interaction with lipid monolayers by measuring surface pressure.
- Assessed liposome aggregation and carboxyfluorescein leakage.
Main Results:
- Synapsin I binding rapidly increased FPE fluorescence, indicating a more positive membrane surface charge.
- Synapsin I binding to lipid monolayers increased surface pressure, dependent on anionic lipids.
- Synapsin I induced rapid liposome aggregation but not carboxyfluorescein leakage.
Conclusions:
- Synapsin I possesses amphipathic amino acid regions enabling electrostatic and hydrophobic membrane interactions.
- These interactions explain synapsin I's high-affinity liposome binding and membrane-stabilizing effects.