DNA Binding Provides a Molecular Strap Activating the Adenovirus Proteinase*□S

Human adenovirus proteinase (AVP) requires two cofac-tors for maximal activity: pVIc, a peptide derived from the C terminus of adenovirus precursor protein pVI, and the viral DNA. Synchrotron protein footprinting was used to map the solvent accessible cofactor binding sites and to identify conformational changes associated with the bind-ing of cofactors to AVP. The binding of pVIc alone or pVIc and DNA together to AVP triggered significant conforma-tional changes adjacent to the active site cleft sand-wiched between the two AVP subdomains. In addition, upon binding of DNA to AVP, it was observed that specific residues on each of the two major subdomains were sig-nificantly protected from hydroxyl radicals. Based on the locations of these protected side-chain residues and con-served aromatic and positively charged residues withi