α-Helical element at the hormone-binding surface of the insulin receptor functions as a signaling element to activate its tyrosine kinase

Jonathan Whittaker, Linda J. Whittaker, Charles T. Roberts, Nelson B. Phillips, Faramarz Ismail-Beigi, Michael C. Lawrence, Michael A. Weiss

    Research output: Contribution to journalArticlepeer-review

    27 Scopus citations

    Abstract

    The primary hormone-binding surface of the insulin receptor spans one face of the N-terminal β-helix of the α-subunit (the L1 domain) and an α-helix in its C-terminal segment (αCT). Crystallographic analysis of the free ectodomain has defined a contiguous dimerrelated motif in which the αCT α-helix packs against L1 β-strands 2 and 3. To relate structure to function, we exploited expanded genetic-code technology to insert photo-activatable probes at key sites in L1 and αCT. The pattern of αCT-mediated photo-cross-linking within the free and bound receptor is in accord with the crystal structure and prior mutagenesis. Surprisingly, L1 photoprobes in β-strands 2 and 3, predicted to be shielded by αCT, efficiently cross-link to insulin. Furthermore, anomalous mutations were identified on neighboring surfaces of αCT and insulin that impair hormone-dependent activation of the intracellular receptor tyrosine kinase (contained within the transmembrane β-subunit) disproportionately to their effects on insulin binding. Taken together, these results suggest that αCT, in addition to its hormone-recognition role, provides a signaling element in the mechanism of receptor activation.

    Original languageEnglish (US)
    Pages (from-to)11166-11171
    Number of pages6
    JournalProceedings of the National Academy of Sciences of the United States of America
    Volume109
    Issue number28
    DOIs
    StatePublished - Jul 10 2012

    Keywords

    • Affinity
    • Alanine scanning
    • Nonstandard mutagenesis

    ASJC Scopus subject areas

    • General

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