title: De novo design of an IL-4 antagonist and its structure at 1.9 A.
abstract: An IL-4 antagonist was designed based on structural and biochemical analysis of unbound IL-4 and IL-4 in complex with its high-affinity receptor (IL-4Ralpha). Our design strategy sought to capture a protein-protein interaction targeting the high affinity that IL-4 has for IL-4Ralpha. This strategy has impact due to the potential relevance of IL-4Ralpha as a drug target in the treatment of asthma. To mimic the IL-4 binding surface, critical side chains for receptor binding were identified, and these side chains were transplanted onto a previously characterized, de novo-designed four-helix protein called designed helical protein 1 (DHP-1). This first-generation design resolved the ambiguity previously described for the connectivity between helices in DHP-1 and resulted in a protein capable of binding to IL-4Ralpha. The second-generation antagonist was based upon further molecular modeling, and it succeeded in binding IL-4Ralpha better than the first-generation. This protein, termed DHP-14-AB, yielded a protein with a cooperative unfolding transition (DeltaGu0=8.1 kcal/mol) and an IC50 of 27 microM when in competition with IL-4 whereas DHP-1 had no affinity for IL-4Ralpha. The crystal structure of DHP-14-AB was determined to 1.9-A resolution and was compared with IL-4. This comparison revealed how design strategies targeting protein-protein interactions require high-resolution 3D data and the incorporation of orientation-specific information at the level of side-chains and secondary structure element interactions.
authors.affiliation: Department of Biochemistry and Biophysics, University of California, 600 16th Street, Box 2240, San Francisco, CA 94143-2240, USA.
authors.forename: Sherry L
authors.initials: SL
authors.lastname: Laporte
authors.forename: Charles M
authors.initials: CM
authors.lastname: Forsyth
authors.forename: Brian C
authors.initials: BC
authors.lastname: Cunningham
authors.forename: Larry J
authors.initials: LJ
authors.lastname: Miercke
authors.forename: David
authors.initials: D
authors.lastname: Akhavan
authors.forename: Robert M
authors.initials: RM
authors.lastname: Stroud
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D015195:Drug Design; D015847:Interleukin-4 / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D015202:Protein Engineering; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry*; D019948:Receptors, Interleukin-4 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: C499757:DHP-14-AB protein; D011506:Proteins; D019948:Receptors, Interleukin-4; D015847:Interleukin-4