CLONING, PURIFICATION, AND PRELIMINARY CHARACTERIZATION BY CIRCULAR-DICHROISM AND NMR OF A CARBOXYL-TERMINAL DOMAIN OF THE BACTERIOPHAGE-P22 SCAFFOLDING PROTEIN

Assembly of double-stranded DNA viruses and bacteriophages involves th e polymerization of several hundred molecules of coat protein, directe d by an internal scaffolding protein. A 163-amino acid carboxyl-termin al fragment of the 303-amino acid bacteriophage P22 scaffolding protei n was cloned, overexpressed, and purified. This fragment is active in procapsid assembly reactions in vitro. The circular dichroism spectrum of the fragment, as well as the 1D-NMR and N-15-(1) HSQC spectra of t he uniformly-labeled protein, indicate that stable secondary structure elements are present. Determination of the three dimensional packing of these elements into the folded scaffolding protein fragment is unde rway. Structured-based drug design targeted at structural proteins req uired for viral assembly may have potential as a therapeutic strategy.