title: Biological activity of covalently-linked insulin-receptor complexes in rat adipocytes. Effect of pH.
abstract: The relative molar potencies of covalently and reversibly-bound insulin-receptor complexes were studied as a function of pH. The insulin derivatives used were 125I-B2 (2-nitro-4-azidophenylacetyl)des-PheB1-insulin and 125I-B29(2-nitro-4-azidophenylacetyl)des-PheB1-insulin. The potencies of both types of reversible complexes were effectively identical and constant between pH 7 and 8. The relative potency of the covalent B2-complex increased from 25 to 75%, and of the covalent B29 complex from 30 to nearly 100%. This indicates that the covalently linked partners in the complex are able to flex about the cross-linkages. Variations in the potency are due to variations in the number of correctly associated, reversibly or covalently bound insulin-receptor complexes. The form of the pH dependance suggests that an ionizable group, possibly an amino group, must be deprotonated to allow effective interaction.
mesh_terms: D000273:Adipose Tissue / Q000502:physiology*; D000818:Animals; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000378:metabolism*; D008055:Lipids / Q000096:biosynthesis; D008297:Male; D051381:Rats; D011972:Receptor, Insulin / Q000502:physiology*; D013329:Structure-Activity Relationship
chemical_list: D007328:Insulin; D008055:Lipids; D011972:Receptor, Insulin