STRUCTURE-BASED DESIGN OF PEPTIDE PRESENTATION ON A VIRAL SURFACE - THE CRYSTAL-STRUCTURE OF A PLANT ANIMAL VIRUS CHIMERA AT 2.8 ANGSTROM RESOLUTION/

Background: We employed a genetically engineered icosahedral plant vir us, cowpea mosaic virus (CPMV), as an expression and presentation syst em to display a 14 amino acid linear antigenic epitope found in a caps id protein of human rhinovirus 14(HRV14). Results: Gram quantities of the CPMV/HRV14 chimera were made in plants and purified particles were crystallized in a form isomorphous with wild-type CPMV, The 2.8 Angst rom resolution structure of the chimera shows that the inserted loop i s well ordered and that if the loop were intact, a phenylalanine resid ue of CPMV would be placed in a hydrophilic environment. The resultant strain may make the loop an attractive substrate for endogenous plant proteases, as roughly 80% of the inserted polypeptides are cleaved, a llowing the phenylalanine to be partially buried, Altering the phenyla lanine to an arginine could relieve the stress, reducing the propensit y for cleavage and increasing the likelihood that the peptide will ass ume a structure closely similar to its structure in HRV14. Conclusions : Successful crystallization of other CPMV chimeras in forms isomorpho us with the native virus suggests that this is a viable system for str ucture-based design of peptide presentation.