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Ca-dependent binding of actin to gelsolin
Sofia Khaitlina1, Horst Hinssen
1Institute of Cytology RAS, St. Petersburg, Russia.
FEBS Letters
|June 18, 2002
Summary
Calcium ions (Ca2+) induce conformational changes in gelsolin, affecting actin binding and complex stability. These findings reveal critical calcium concentrations for gelsolin
Area of Science:
- Biochemistry
- Molecular Biology
- Biophysics
Background:
- Gelsolin is a calcium-dependent actin-binding protein.
- Its interaction with actin is crucial for cellular processes like cell motility and cytokinesis.
- Understanding the precise role of calcium in gelsolin's conformational changes and actin interactions is essential.
Purpose of the Study:
- To investigate the effects of varying calcium concentrations on gelsolin conformation.
- To determine the calcium requirements for actin monomer binding to gelsolin.
- To elucidate the calcium dependence of actin-gelsolin complex stability.
Main Methods:
- Limited proteolysis (tryptic cleavage) to probe gelsolin conformation.
- Monitoring pyrene-labeled actin fluorescence to assess actin binding.
- Analysis of ternary actin/gelsolin complex stability at different calcium levels.
Main Results:
- Calcium concentrations between 0.3-1.0 microM expose tryptic cleavage sites in gelsolin, indicating a conformational change.
- A single actin monomer binds to gelsolin's N-terminal half at these low calcium levels.
- Gelsolin-mediated enhancement of pyrene actin fluorescence requires >50 microM Ca(2+).
- A preformed 2:1 actin/gelsolin complex is stable only above 30 microM Ca(2+).
Conclusions:
- Calcium ions induce a transition of gelsolin from a closed to an open conformation between 3 x 10(-7) to 10(-6) M.
- Stabilization of actin-actin contacts within the 2:1 actin/gelsolin complex requires calcium concentrations greater than 10(-5) M.