Insulin-like growth factor amino acid sequence

Amino acids are linked together by peptides, some of which are the body s vital nitrogenic compounds. For instance, Growth Hormone, Insulin, and Insulin-Like-Growth-Factor-1 are specific sequences of amino acids. 

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. 

RIO. Rinderknecht, E., and Humbel, R. E., The amino acid sequence of insulin-like growth factor I and its structural homology with proinsulin. /. Biol. Chem. 253, 2769-2776 (1978). 

Amino acid sequence analyses reveal the existence of more than 50 different growth factor receptors. These can be grouped into at least 18 families, notable examples of which include the (1) platelet-derived growth factor receptor family, (2) fibroblast growth factor receptor family, (3) epidermal growth factor receptor family, and (4) insulin-like growth factor receptor family. 

More recently, manipulation of the structure of the B-chain, aiming at decreasing the potential for P-sheet interactions of the peptide backbone between insulin monomers, has also resulted in insulins with decreased tendency to self-associate. Examples of such analogs are the LysPro insulin (Brems et al, 1992), in which the B28 and B29 residues are interchanged, as is the case in insulin-like growth factor-I, and analogs characterized by deletion of one of the amino acid residues in the B25 B28 sequence (Balschmidt and Brange, 1992). 

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