title: Molecular Probing of the HPV-16 E6 Protein Alpha Helix Binding Groove with Small Molecule Inhibitors.
abstract: The human papillomavirus (HPV) HPV E6 protein has emerged as a central oncoprotein in HPV-associated cancers in which sustained expression is required for tumor progression. A majority of the E6 protein interactions within the human proteome use an alpha-helix groove interface for binding. The UBE3A/E6AP HECT domain ubiquitin ligase binds E6 at this helix-groove interface. This enables formation of a trimeric complex with p53, resulting in destruction of this tumor suppressor. While recent x-ray crystal structures are useful, examples of small molecule probes that can modulate protein interactions at this interface are limited. To develop insights useful for potential structure-based design of ligands for HPV E6, a series of 2,6-disubstituted benzopyranones were prepared and tested as competitive antagonists of E6-E6AP helix-groove interactions. These small molecule probes were used in both binding and functional assays to evaluate recognition features of the E6 protein. Evidence for an ionic functional group interaction within the helix groove was implicated by the structure-activity among the highest affinity ligands. The molecular topographies of these protein-ligand interactions were evaluated by comparing the binding and activities of single amino acid E6 mutants with the results of molecular dynamic simulations. A group of arginine residues that form a rim-cap over the E6 helix groove offer compensatory roles in binding and recognition of the small molecule probes. The flexibility and impact on the overall helix-groove shape dictated by these residues offer new insights for structure-based targeting of HPV E6.
authors.affiliation: Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America.
authors.forename: Anne
authors.initials: A
authors.lastname: Rietz
authors.affiliation: Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, Indiana, United States of America.
authors.forename: Dino P
authors.initials: DP
authors.lastname: Petrov
authors.affiliation: Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, Indiana, United States of America.
authors.forename: Matthew
authors.initials: M
authors.lastname: Bartolowits
authors.affiliation: Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America.
authors.forename: Marsha
authors.initials: M
authors.lastname: DeSmet
authors.affiliation: Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, Indiana, United States of America.
authors.forename: V Jo
authors.initials: VJ
authors.lastname: Davisson
authors.affiliation: Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America.
authors.forename: Elliot J
authors.initials: EJ
authors.lastname: Androphy
mesh_terms: D001578:Benzopyrans / Q000737:chemistry* / Q000494:pharmacology*; D057927:Hydrophobic and Hydrophilic Interactions; D056004:Molecular Dynamics Simulation; D015335:Molecular Probes / Q000737:chemistry* / Q000494:pharmacology*; D009856:Oncogene Proteins, Viral / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D012097:Repressor Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001578:Benzopyrans; C068651:E6 protein, Human papillomavirus type 16; D015335:Molecular Probes; D009856:Oncogene Proteins, Viral; D012097:Repressor Proteins