Intermolecular phosphorylation between insulin holoreceptors does not stimulate substrate kinase activity.
We photocoupled benzoylphenylalanineB25, B29 epsilon-biotin insulin (BBpa-insulin) to native insulin receptors to obtain a uniform receptor population with covalently bound, non-dissociable ligand. We employed BBpa-insulin-bound and autophosphorylated (activated) receptor to phosphorylate substrate insulin receptor under conditions where the substrate receptor never interacts with insulin. The substrate receptor becomes phosphorylated in this inter-receptor fashion and reaches a phosphorylation state 50% of the maximal obtainable by autophosphorylation. However, this phosphorylation does not activate the substrate receptor to any measurable degree. We conclude that intermolecular phosphorylation of the insulin holoreceptors is unlikely to be of physiological significance.
Lee
J
J
Department of Biochemistry, Boston University, School of Medicine, Massachusetts 02118, USA.
Shoelson
S E
SE
Pilch
P F
PF
D016475:3T3 Cells; D000818:Animals; D001710:Biotin / Q000031:analogs & derivatives / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000031:analogs & derivatives / Q000378:metabolism; D051379:Mice; D010766:Phosphorylation; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism*; D013379:Substrate Specificity
C079861:B29-biotin insulin; D007328:Insulin; D001710:Biotin; D020794:Receptor Protein-Tyrosine Kinases; D011972:Receptor, Insulin