Answer:
on a tyrosine residue
bind to insulin
Explanation:
The insulin receptor substrate-1 (IRS1) is a signaling protein that can be phosphorylated on multiple tyrosine and serine/threonine residues. IRS1 contains several conserved domains including a pleckstrin (PH) domain and a PTB domain involved in protein phosphorylation and ligand binding. In the first place, IRS1 is phosphorylated on a tyrosine residue, and then IRS1 binds to insulin or the insulin-like growth factor-1 (IGF-1), thereby activating transduction pathways such as, for example, MAPK/ERK. Moreover, RS1 is also phosphorylated on serine residues, thereby triggering opposite effects in insulin-associated signaling.
