How many pas are there in insulin receptor ?
An insulin receptor has 4 pas. It is a tetramer made up of two a and two b subunits. The a subunit are extracellular, whereas the b subunit penetrate through the cell membranes into the cytoplasm. The intracellular poions of the b subunits have tyrosine kinase activity. Once insulin binds to the alpha subunits, the poion of the beta subunits protruding into the cell become autophosphorylated. Autophosphorylation of the beta subunits in turn activates a local tyrosine kinase, which causes phophorylation of multiple intracellular enzymes. The net effect is to activate some of these enzymes while inactivating others. Ref: Guyton and Hall 13th edition PGno: 984
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Endocrinology