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The initial fusion pore induced by baculovirus GP64 is large and forms quickly
1Laboratory of Cellular and Molecular Biosphysics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-1855, USA.
The Journal of Cell Biology
|December 1, 1996
Summary
Baculovirus GP64-mediated cell fusion differs from other fusion types. Unlike typical flickering pores, GP64 fusion pores are stable, have high initial conductance, and short lag times, suggesting a distinct lipid-lined, barrel-shaped pore model.
Area of Science:
- Membrane biology
- Biophysics
- Cellular fusion mechanisms
Background:
- Fusion pore formation is the initial event in membrane fusion.
- Previously studied fusion pores exhibit flickering, fluctuating stages, and long lag times.
- Baculovirus GP64 protein mediates Sf9 cell-cell fusion.
Purpose of the Study:
- To investigate the characteristics of fusion pores formed during baculovirus GP64-mediated cell-cell fusion.
- To compare GP64-mediated fusion pores with those observed in exocytosis and viral fusion.
- To determine the structural and kinetic properties of the initial GP64 fusion pore.
Main Methods:
- Utilized double whole-cell recording for high time-resolution measurements.
- Employed time-resolved admittance recordings for fusion pore conductance calculations.
- Analyzed waiting time distributions to model pore formation kinetics.
Main Results:
- GP64-mediated fusion pores showed abrupt formation with wide initial conductance distribution (~1 nS).
- Initial fusion pore conductances were often stable for extended periods (up to a minute).
- Fusion pores exhibited minimal fluctuations and lag times typically less than 1 second.
Conclusions:
- GP64-mediated fusion pores are distinct, lacking flickering and exhibiting stable, high conductance.
- The pore formation kinetics suggest a model involving multiple independent elements (~19).
- Findings support a barrel-shaped pore model composed of GP64 trimers and lipids.