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Interfacial basic cluster in annexin V couples phospholipid binding and trimer formation on membrane surfaces.
Youde Mo1, Begoña Campos, Tanya R Mealy
1Department of Physiology and Biophysics, Boston University School of Medicine, Massachusetts 02118, USA.
The Journal of Biological Chemistry
|October 29, 2002
Summary
This study reveals that specific basic residues in annexin V are crucial for binding to phospholipid membranes. Arg(23) is identified as a key determinant for this interaction and subsequent protein trimerization.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Annexin V is a eukaryotic protein known for calcium-dependent binding to phospholipid membranes.
- Understanding the molecular mechanisms of annexin V-membrane interactions is vital for cell biology.
Purpose of the Study:
- To investigate the functional role of interfacial basic residues in annexin V's phospholipid membrane binding.
- To elucidate the structural basis of annexin V's membrane interaction and trimerization.
Main Methods:
- Site-directed mutagenesis was employed to create four annexin V mutants (R23E, K27E, R61E, R149E).
- X-ray crystallography was used to determine the structures of wild-type and mutant proteins.
- Solution liposome binding assays were performed to quantify membrane adsorption.
Main Results:
- All four mutants showed significantly reduced phospholipid membrane adsorption compared to wild-type annexin V.
- The R23E mutation had the most pronounced effect, severely impairing membrane binding.
- Crystal structures revealed local changes in salt bridges, particularly involving Arg(23), which is critical for trimer formation.
Conclusions:
- The interfacial basic cluster in annexin V, especially Arg(23), is essential for effective phospholipid binding.
- Trimerization of annexin V on the membrane surface is synergistically coupled with phospholipid binding at this basic cluster.