Published Online: 15 SEP 2006
Copyright © 2006 Wiley-VCH Verlag GmbH & Co. KGaA
Encyclopedia of Molecular Cell Biology and Molecular Medicine
How to Cite
Creutz, C. E. 2006. Annexins. Encyclopedia of Molecular Cell Biology and Molecular Medicine.
- Published Online: 15 SEP 2006
The annexins are a family of structurally related, calcium-dependent, phospholipid-binding proteins that have been postulated to mediate calcium-dependent activities at membrane surfaces such as membrane fusion, lipid metabolism and reorganization, and ion permeation. The basic annexin structure consists of 4 homologous 70–amino acid repeats and a unique N-terminal domain. These repeats do not contain sequences found in other intracellular calcium-binding proteins; therefore, the annexins represent a novel class of calcium-binding proteins. The “core” domains of all the annexins, composed of the four 70–amino acid repeats, are 40 to 60% identical in sequence. One annexin family member (annexin VI) has been formed as a result of gene duplication and consists of 8 of the 70–amino acid repeats. Another type of duplication has occurred with annexin II (calpactin), in which two 36-kDa molecules, the “heavy chains,” each containing four repeats, bind to a dimer of a 10-kDa protein, the “light chains,” to form a tetramer. In contrast to other lipid-binding proteins such as protein kinase C, or phospholipase A2, the annexins are unique in that most are bivalent. That is, they can attach to two membranes, rather than just one, and as a consequence, draw them together.
- Membrane Fusion;