Extending 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: 10.1074/jbc.M116.761015
- 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 ...
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.
From the Department of Chemistry, University of Basel, Klingelbergstrasse 80 CH-4056 Basel, Switzerland.,the Departments of Biochemistry, email@example.com.,From the Department of Chemistry, University of Basel, Klingelbergstrasse 80 CH-4056 Basel, Switzerland, firstname.lastname@example.org.,the Departments of Biochemistry.,the Department of Medical Biology, University of Melbourne, Parkville, Victoria 3010, Australia.,Medicine, and.,the The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, Australia, and.,the La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia.,Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio 44106.