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Annexins possess functionally distinguishable Ca2+ and phospholipid binding domains
1Department of Medicine, University of California, San Francisco 94143-0868.
Biochemical and Biophysical Research Communications
|April 29, 1994
Summary
Distinct domains in annexins control calcium (Ca2+) requirements and affinity for phospholipids like phosphatidylserine (PS). Repeat 1 primarily dictates PS binding affinity, while other repeats influence Ca2+ levels needed for binding.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Annexins are Ca2+-dependent phospholipid-binding proteins.
- Annexin I and Annexin V exhibit different affinities for phosphatidylserine (PS) and varying Ca2+ requirements for binding.
Purpose of the Study:
- To identify the structural domains responsible for differential Ca2+ requirements and PS binding affinities in annexins.
- To elucidate the structure-function relationships governing annexin-phospholipid interactions.
Main Methods:
- Construction and characterization of chimeric annexins.
- Analysis of Ca2+ dependence and affinity for PS vesicles.
Main Results:
- A chimera with Annexin V's repeat 1 and Annexin I's other repeats showed Annexin I-like Ca2+ requirements.
- Chimeras with Annexin I's repeat 1 and Annexin V's other repeats exhibited Annexin V-like Ca2+ requirements.
- The source of repeat 1 determined overall PS binding affinity, with Annexin V's repeat 1 conferring higher affinity.
Conclusions:
- The Ca2+ requirement for annexin phospholipid binding is regulated by distinct domains from those controlling overall phospholipid affinity.
- Repeat 1 of annexins is a key determinant of phosphatidylserine binding affinity.