Download MendeleyExtending Halogen-based Medicinal Chemistry to Proteins: IODO-INSULIN AS A CASE STUDY.
El Hage, K., Pandyarajan, V., Phillips, N.B., Smith, B.J., Menting, J.G., Whittaker, J., Lawrence, M.C., Meuwly, M., Weiss, M.A.(2016) J Biol Chem 291: 27023-27041
- PubMed: 27875310
- DOI: https://doi.org/10.1074/jbc.M116.761015
- Primary Citation of Related Structures:
5EMS - PubMed Abstract:
Insulin, a protein critical for metabolic homeostasis, provides a classical model for protein design with application to human health. Recent efforts to improve its pharmaceutical formulation demonstrated that iodination of a conserved tyrosine (Tyr B26 ) enhances key properties of a rapid-acting clinical analog. Moreover, the broad utility of halogens in medicinal chemistry has motivated the use of hybrid quantum- and molecular-mechanical methods to study proteins. Here, we (i) undertook quantitative atomistic simulations of 3-[iodo-Tyr B26 ]insulin to predict its structural features, and (ii) tested these predictions by X-ray crystallography. Using an electrostatic model of the modified aromatic ring based on quantum chemistry, the calculations suggested that the analog, as a dimer and hexamer, exhibits subtle differences in aromatic-aromatic interactions at the dimer interface. Aromatic rings (Tyr B16 , Phe B24 , Phe B25 , 3-I-Tyr B26 , and their symmetry-related mates) at this interface adjust to enable packing of the hydrophobic iodine atoms within the core of each monomer. Strikingly, these features were observed in the crystal structure of a 3-[iodo-Tyr B26 ]insulin analog (determined as an R 6 zinc hexamer). Given that residues B24-B30 detach from the core on receptor binding, the environment of 3-I-Tyr B26 in a receptor complex must differ from that in the free hormone. Based on the recent structure of a "micro-receptor" complex, we predict that 3-I-Tyr B26 engages the receptor via directional halogen bonding and halogen-directed hydrogen bonding as follows: favorable electrostatic interactions exploiting, respectively, the halogen's electron-deficient σ-hole and electronegative equatorial band. Inspired by quantum chemistry and molecular dynamics, such "halogen engineering" promises to extend principles of medicinal chemistry to proteins.
Organizational Affiliation:
From the Department of Chemistry, University of Basel, Klingelbergstrasse 80 CH-4056 Basel, Switzerland.
