Copine Explained

In molecular biology, copines is a name for the group of human proteins that includes members such as CPNE1, CPNE4, CPNE6, and CPNE8.^[1] These are highly conserved, calcium-dependent membrane proteins found in a variety of eukaryotes.^[2] The domain structure of these 55 kDa ^[3] proteins suggests that they may have a role in membrane trafficking in some prokaryotes as well as eukaryotes.^[4] Copines contains two C2 domains which play a role in signal transduction by binding to calcium, phospholipids, or polyphosphates. Both domains are located at the N-terminal portion of the protein which is not the case for most other double C2 domain proteins, and their role is most similar to that carried out by proteins that exhibit a single C2 domain.^[5] The core domain located at the C-terminus part of the copine is found to have a unique and conserved primary sequence. The function of the core domain is still uncertain, however, researchers believe it has a similar function to the "A domain" in integrins. This similarity in function involves serving as a binding site for target proteins, and is supported by evidence that the copine core domain exhibits secondary and tertiary structures comparable to the integrin A domain.

Notes and References

1. Web site: copine family. UniProtKB. 28 March 2013.
2. Damer CK, Bayeva M, Hahn ES, Rivera J, Socec CI . Copine A, a calcium-dependent membrane-binding protein, transiently localizes to the plasma membrane and intracellular vacuoles in Dictyostelium . BMC Cell Biology . 6 . 46 . December 2005 . 16343335 . 1327671 . 10.1186/1471-2121-6-46 . free .
3. Tomsig JL, Creutz CE . Biochemical characterization of copine: a ubiquitous Ca2+-dependent, phospholipid-binding protein . Biochemistry . 39 . 51 . 16163–16175 . December 2000 . 11123945 . 10.1021/bi0019949 .
4. Creutz CE, Tomsig JL, Snyder SL, Gautier MC, Skouri F, Beisson J, Cohen J . The copines, a novel class of C2 domain-containing, calcium-dependent, phospholipid-binding proteins conserved from Paramecium to humans . The Journal of Biological Chemistry . 273 . 3 . 1393–1402 . January 1998 . 9430674 . 10.1074/jbc.273.3.1393 . free .
5. Damer CK, Bayeva M, Kim PS, Ho LK, Eberhardt ES, Socec CI, Lee JS, Bruce EA, Goldman-Yassen AE, Naliboff LC . 6 . Copine A is required for cytokinesis, contractile vacuole function, and development in Dictyostelium . Eukaryotic Cell . 6 . 3 . 430–442 . March 2007 . 17259548 . 1828924 . 10.1128/EC.00322-06 .