Insulin receptor homologues

Homologues of the mammalian insulin receptor, IR, are the DAF-2 receptor in Caenorhabditis elegans and the IR-like receptor in Drosophila. TTie DAF-2 receptor shares 35% of its amino-acid sequence with the human insulin receptor and 34% with the insulin-like growth factor receptor-1. The tyrosine kinase domain of the DAF-2 receptor is 70% similar and 50% identical to the tyrosine kinase domain of the human insulin receptor. A ligand for DAF-2 has not yet been identified, but an insulin-like peptide is anticipated. Since a t5T>ical insulin receptor substrate, like lRS-1 or IRS-2, has not been found in C. elegans, it is assumed that a COOH-terminal extension of the DAF-2 receptor serves as a built-in receptor substrate, which when phosphorylated, helps to recruit signalling proteins. 

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