Tryptic peptide analysis and NH2 -terminal amino acid sequences of polyhedrins of two baculoviruses from Orgyia pseudotsugata

Comparative analysis of the tryptic peptides and terminal amino acid sequence was made on polyhedrins from two genetically different baculoviruses that are naturally pathogenic for the same insect host. Comparison of the tryptic peptides of the nucleopolyhedrosis bundle virus and nucleopolyhedrosis single-rod virus of Orgyia pseudotsugata by means of cation-exchange resins indicated that the proteins have a closely related amino acid sequence. The NH 2 -terminal amino acid sequence of polyhedrins from the two viruses differed in only 4 out of 34 amino acids. The nucleopolyhedrosis bundle virus and the nucleopolyhedrosis single-rod virus also differed in 4 and 5 out of 34 terminal amino acids, respectively, from the sequence reported for polyhedrin of a baculovirus of Bombyx mori [Serebryani, S. B., Levitina, T. L., Kautsman, M. L., Radavski, Y. L., Gusak, N. M., Ovander, M. N., Sucharenko, N. V. & Kozlov, E. A. (1977) J. Invertebr. Pathol. 30, 442-443]. In addition, the nucleopolyhedrosis single-rod virus had two amino acids (Met-Tyr) on the NH 2 terminus that were not present on the terminus of nucleopolyhedrosis bundle virus or B. mori baculovirus polyhedrin. Approximately half (six) of the total tyrosine residues are clustered in the terminal 20 amino acids of the polyhedrins. Secondary structures predicted from the primary sequence suggest that the tyrosines are clustered in two areas. This nonrandom distribution and the pK a of about 10 for tyrosine may be related to the alkali solubility of the polyhedrin. baculovirus polyhedrin structure genetic stability