BpaB25 insulins: Photoactivatable analogues that quantitatively cross-link, radiolabel, and activate the insulin receptor

Steven E. Shoelson, Jongsoon Lee, Claire S. Lynch, Jonathan M. Backer, Paul F. Pilch

Research output: Contribution to journalArticle

54 Citations (Scopus)

Abstract

Benzoylphenylalanine (Bpa), a photoactivatable amino acid was incorporated into the 25 position of the insulin B-chain by a combination of chemical synthesis and enzymatic semisynthesis. BpaB25 insulin binds specifically to the insulin receptor with an affinity ≈40% that of native insulin. Addition of biotin or ε-amino-hexanoic acid-iminobiotin at the ε-LysB29 position to form BpaB25,B29ε-biotinyl (BBpa) or BpaB25,B29ε-(Aha-iminobiotin) analogues had little adverse effect on receptor binding affinity and provided a convenient handle for affinity purification, gel shift assays, and blotting of cross-linked complexes with avidin. The analogues were readily 125I-iodinated with the major-ity of 125I being incorporated at the TyrA14 position; the monoiodo-A14 derivative was easily separated from other forms by high performance liquid chromatography. Photolysis of a complex of the insulin receptor and either BpaB25 insulin or [125I]iodo-TyrA14,BpaB25 insulin yields a covalent insulin-receptor complex. The efficiency of cross-linking with these reagents was unusually high, ranging from 60 to 100%. Furthermore, cross-linking to the insulin receptor results in kinase activation in vitro, and in intact cells insulin receptor phosphorylation and internalization were both activated. Notably, even at saturating concentrations one molecule of BpaB25 insulin covalently cross-linked each α2β2 receptor, demonstrating that holoreceptor activation occurs with one high affinity insulin binding site occupied and, if a second insulin binds with lower affinity it must be in a different orientation. Bpa insulin analogues form a new class of photoaffinity reagents which facilitate studies relating insulin-insulin receptor structure and function.

Original languageEnglish (US)
Pages (from-to)4085-4091
Number of pages7
JournalJournal of Biological Chemistry
Volume268
Issue number6
StatePublished - Feb 25 1993
Externally publishedYes

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Insulins
Insulin Receptor
Insulin
Chemical activation
Cross-Linking Reagents
Phosphorylation
Avidin
Photolysis
High performance liquid chromatography
Biotin
Purification
Assays
Phosphotransferases
Gels
Binding Sites
High Pressure Liquid Chromatography

ASJC Scopus subject areas

  • Biochemistry

Cite this

BpaB25 insulins : Photoactivatable analogues that quantitatively cross-link, radiolabel, and activate the insulin receptor. / Shoelson, Steven E.; Lee, Jongsoon; Lynch, Claire S.; Backer, Jonathan M.; Pilch, Paul F.

In: Journal of Biological Chemistry, Vol. 268, No. 6, 25.02.1993, p. 4085-4091.

Research output: Contribution to journalArticle

Shoelson, Steven E. ; Lee, Jongsoon ; Lynch, Claire S. ; Backer, Jonathan M. ; Pilch, Paul F. / BpaB25 insulins : Photoactivatable analogues that quantitatively cross-link, radiolabel, and activate the insulin receptor. In: Journal of Biological Chemistry. 1993 ; Vol. 268, No. 6. pp. 4085-4091.
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