| ADAM13 was first described as a protein expressed in somatic mesoderm and neural crest cells, in developing Xenopus embryos. ADAM13 was also found in liver, heart, and intestines from adult Xenopus. ADAM13 may regulate cellular signaling via Src and Src tyrosine kinase. ADAM13 may also act as a cell attachment molecule, by binding integrins through the cysteine rich domain amoung many other roles. A member of the metalloproteinase family containing disintegrin like domains (ADAMs) the functions of ADAM13 are still poorly understood. ADAM13 contains the canonical HExxHxxxxxH zinc metalloproteinase motif, as well as disintegrin, cysteine rich, EFG like, transmembrane and Cytoplasmic domains. ADAM13 has been shown to be proteolytically active, cleaving fibronectin after binding it to the EGF like domain. ADAM13 is also shed from cells in culture, cleaved aminoterminal from the transmembrane domain, and is released into the culture media. Shed ADAM13 is a 52 kD protein, and can form complexes with a2 macroglobulin, suggesting it is a competent protease. Xenopus ADAM13 has greatest homology with human ADAM 33 (51% identical), and is 46% identical with human or mouse ADAM12 or ADAM19. It is still unclear if any of these ADAMs are species orthologs of Xenopus ADAM13, but there are significant differences between the related sequences, suggesting that ADAM13 may be a unique protein. The full length Xenopus ADAM13 sequence codes for a 914 amino acid protein. Predicted mass is 99.749 kD, but glycosylation and cyteine rich regions give Xenopus ADAM13 an apparent MW of 120 kD unprocessed, and 97 kD processed forms, on reduced SDS PAGE gels. ADAM13 contains a putative furin cleavage site, suggesting that a prohormone convertase cleaves the propeptide domain away from the catalytic domain |
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