Cloning and characterization of a cDNA encoding bovine endonexin (chromobindin 4).

Endonexin is a 32kDa, calcium-dependent membrane-binding protein that is one of a group of proteins that binds to chromaffin granule membranes and may regulate membrane fusion events occurring during exocytosis. In this study an oligonucleotide probe that codes for a highly conserved, repeated sequence present in this and related proteins was used to isolate a 2,048 nucleotide cDNA encoding endonexin from a bovine liver cDNA library. The translated amino acid sequence of endonexin shows the four domain structure characteristic of proteins in this class. The nucleotide sequence is 55 to 61% identical to that of the related membrane-binding proteins lipocortin, calpactin, endonexin II and (half of) 68kDa calelectrin. Southern blot analysis of bovine genomic DNA suggests the presence of a single gene for this protein. A consensus nucleotide sequence (TCTGGGAACTTC) was identified in the 5' nontranslated portion of the endonexin mRNA that is also represented in the messages for calpactin and endonexin II.