Specific phosphorylation of membrane proteins of Mr 44,000 and Mr 32,000 by the autophosphorylated insulin receptor from the hepatopancreas of the shrimp Penaeus monodon (Crustacea: Decapoda).

Abstract

The insulin receptor, purified from the hepatopancreas of the shrimp Penaeus monodon, is a hydrophobic heterodimer of subunits with relative masses (Mr) of 70,000 and 58,000, as estimated by FPLC on Superose 12 and SDS-PAGE. Only the subunit of Mr 70,000 was autophosphorylated after the addition of insulin. The autophosphorylation occurred specifically at Tyr residues, as demonstrated by the specific subsequent dephosphorylation by the phosphotyrosyl protein phosphatase from the hepatopancreas of the shrimp Penaeus monodon. Proteins of Mr 44,000 and Mr 32,000 on the plasma membrane from the hepatopancreas of the shrimp Panaeus monodon were phosphorylated by the autophosphorylated insulin receptor from the shrimp hepatopancreas, but not by that from the human placenta. The detergent, Triton X-100, caused noticeable enhancement of the autophosphorylation of both shrimp and human insulin receptors.