Regulation of a viral proteinase by a peptide and DNA in one-dimensional space: II. adenovirus proteinase is activated in an unusual one-dimensional biochemical reaction

Background: pVIc, an 11-amino acid peptide from the C terminus of adenovirus precursor protein pVI, activates the adenovirus proteinase (AVP). Results: pVI slides on DNA into AVP, which excises and then covalently binds pVIc thereby rendering AVP fully active. Conclusion: Activation of AVP requires pVI in cis on DNA. Significance: These results indicate a new way a protein substrate interacts with a proteinase, via one-dimensional diffusion on DNA. Late in an adenovirus infection, the viral proteinase (AVP) becomes activated to process virion precursor proteins used in virus assembly. AVP is activated by two cofactors, the viral DNA and pVIc, an 11-amino acid peptide originating from the C terminus of the precursor protein pVI. There is a conundrum in the activation of AVP in that AVP and pVI are sequence-independent DNA-binding proteins with nM equilibrium dissociation constants such that in the virus particle, they are predicted to be essentially irreversibly bound to the viral DNA. Here, we resolve that conundrum by showing that activation of AVP takes place on the one-dimensional contour of DNA. In vitro, pVI, a substrate, slides on DNA via one-dimensional diffusion, D1 1.45 106 bp2/s, until it binds to AVP also on the same DNA molecule. AVP, partially activated by being bound to DNA, excises pVIc, which binds to the AVP molecule that cut it out. pVIc then forms a disulfide bond with AVP forming the fully active AVP-pVIc complex bound to DNA. In vivo, in heat-disrupted immature virus, AVP was also activated by pVI in DNA-dependent reactions. This activation mechanism illustrates a new paradigm for virion maturation and a new way, by sliding on DNA, for bimolecular complexes to form among proteins not involved in DNA metabolism.