Identification of an amino acid essential to the normal assembly of Autographa californica nuclear polyhedrosis virus polyhedra.

We compared the DNA sequence of the Autographa californica nuclear polyhedrosis virus polyhedrin gene with that of the polyhedrin gene from a morphology mutant called M5. A single point mutation was found at the BamHI restriction site within the polyhedrin coding sequence. This point mutation caused a substitution of leucine for proline at amino acid 58 in the M5 polyhedrin. This point mutation was shown to be responsible for both the appearance of cubic polyhedra and the altered mobility of the polypeptide on sodium dodecyl sulfate-polyacrylamide gels by transferring the M5 polyhedrin gene to the wild-type virus by cotransfection. Recombinants were found which assembled cubic polyhedra in infected cells, had the BamHI restriction site missing, and had an altered mobility of their polyhedrin polypeptide. Computed-predicted secondary-structure analysis indicated that the amino acid at position 58 could be critical to the proper folding of polyhedrin.