Biophysical characterization of the complex between human papillomavirus E6 protein and synapse-associated protein 97

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Celestine Ngang Chi, Anders Bach, Åke Engström, Kristian Strømgaard, Patrik Lundström, Neil Ferguson, Per Jemth

The E6 protein of human papillomavirus exhibits complex interaction patterns with several host proteins and their roles in HPV mediated oncogenesis have proved challenging to study. Here we use several biophysical techniques to explore the binding of E6 to the three PDZ domains of the tumor suppressor protein SAP97. All potential binding sites in SAP97 bind E6 with micromolar affinity. The dissociation rate constants govern the different affinities of HPV16 and HPV18 E6 for SAP97. Unexpectedly, binding is not mutually exclusive and all three PDZ domains can simultaneously bind E6. Intriguingly, this quaternary complex has the same apparent hydrodynamic volume as the unliganded PDZ region, suggesting that a conformational change occurs in the PDZ region upon binding, a conclusion supported by kinetic experiments. Using NMR, we discovered a new mode of interaction between E6 and PDZ: a subset of residues distal to the canonical binding pocket in the PDZ2 domain exhibited non-canonical interactions with the E6 protein. This is consistent with a larger proportion of the protein surface defining binding specificity, as compared to that previously reported.
Original languageEnglish
JournalJournal of Biological Chemistry
Volume286
Issue number5
Pages (from-to)3597-3606
ISSN0021-9258
DOIs
Publication statusPublished - 4 Feb 2011

ID: 32320949