Download MendeleyChiral mutagenesis of insulin's hidden receptor-binding surface: structure of an allo-isoleucine(A2) analogue.
Xu, B., Hua, Q.X., Nakagawa, S.H., Jia, W., Chu, Y.C., Katsoyannis, P.G., Weiss, M.A.(2002) J Mol Biol 316: 435-441
- PubMed: 11866509
- DOI: https://doi.org/10.1006/jmbi.2001.5377
- Primary Citation of Related Structures:
1KMF - PubMed Abstract:
The hydrophobic core of vertebrate insulins contains an invariant isoleucine residue at position A2. Lack of variation may reflect this side-chain's dual contribution to structure and function: Ile(A2) is proposed both to stabilize the A1-A8 alpha-helix and to contribute to a "hidden" functional surface exposed on receptor binding. Substitution of Ile(A2) by alanine results in segmental unfolding of the A1-A8 alpha-helix, lower thermodynamic stability and impaired receptor binding. Such a spectrum of perturbations, although of biophysical interest, confounds interpretation of structure-activity relationships. To investigate the specific contribution of Ile(A2) to insulin's functional surface, we have employed non-standard mutagenesis: inversion of side-chain chirality in engineered monomer allo-Ile(A2)-DKP-insulin. Although the analogue retains native structure and stability, its affinity for the insulin receptor is impaired by 50-fold. Thus, whereas insulin's core readily accommodates allo-isoleucine at A2, its activity is exquisitely sensitive to chiral inversion. We propose that the Ile(A2) side-chain inserts within a chiral pocket of the receptor as part of insulin's hidden functional surface.
Organizational Affiliation:
Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4935, USA.
