Seth Y. Young

Degradation of matrix protein from a nuclear-polyhedrosis virus of Trichoplusia ni by an endogenous protease

Abstract The intact matrix protein of a nuclear-polyhedrosis virus of Trichoplusia ni could be isolated when a contaminating endogenous protease was inhibited by Hg 2+ . The subunit molecular weight of the intact matrix protein was approximately 28,000. When the protease was not inhibited, the matrix protein was degraded to a mixture of peptides which had a strong tendency to self-associate. The protease-degraded matrix protein preparation could be dissociated by 1.0 M formic acid into a single peptide and a peptide aggregate. The sum of the amino acid compositions of the peptide and peptide aggregate was identical, within experimental error, with the amino acid composition of the intact matrix protein.

Isolation and some properties of components of nuclear polyhedra from the cabbage looper, Trichoplusia ni

Abstract Nuclear polyhedra obtained from diseased cabbage looper, Trichoplusia ni, were digested with sodium carbonate-saline buffer, pH 11.0. The dissolved polyhedra formed 3 general zones when subjected to density gradient centrifugation. The slowest sedimenting component (Zone 1) had an ultraviolet absorption curve typical of protein and a sedimentation coefficient of 11 S. Capsids, 310 × 40 nm, were located in Zone 2. Virus particles were found in 1–3 bands (Zone 3); those with envelopes measured 300 × 72 nm, and those without envelopes measured 300 × 33 nm. Virus preparations stained with phosphotungstic acid at pH 7.0 exhibited extensive disruption whereas preparations stained at pH 3.0 did not. Virus particles in the sodium carbonate-saline-digested polyhedra had a sedimentation coefficient of 1228 S. Virus particles isolated by high speed centrifugation had a sedimentation coefficient of 1530 S.

Hemolymph proteins of Trichoplusia ni during the course of a nuclear polyhedrosis virus infection

Abstract Hemolymph proteins of fifth instar larvae of the cabbage looper, Trichoplusia ni, were investigated during the course of a nuclear polyhedrosis virus infection. The concentration of hemolymph protein in diseased larvae was found to be lower than in healthy larvae throughout the course of the disease. While protein in healthy larvae increased rapidly during the fifth instar, that in diseased larvae increased only slightly until the 3rd day and dropped sharply on the 4th day during late stages of the disease. Disc electrophoresis of the hemolymph on 7% acrylamide gels showed this decrease in protein concentration to be due primarily to several major protein fractions of high molecular weight which in healthy larvae increased in concentration during the fifth instar. Selective staining techniques revealed that these were primarily conjugates of glycoprotein and lipoprotein. An additional band of lipoprotein also was present late in the course of the disease which migrated very little in the small pore gels. An investigation of enzyme activity in hemolymph showed two bands of alkaline phosphatase in diseased larvae but only one band in healthy larvae. No differences could be detected in the patterns of esterases, leucine aminopeptidase, or malic dehydrogenase.

Immunoelectrophoresis of hemolymph of the cabbage looper, Trichoplusia ni, during the course of a nuclear polyhedrosis virus infection.

Larvae of the cabbage looper, Trichoplusia ni, were infected with a nuclear polyhedrosis virus and the protein patterns of the hemolymph followed throughout the course of the disease by immunoelectrophoresis. There was a decrease in the protein concentration of the hemolymph which appeared to be due to the loss of two normal protein components and to a reduction in the concentration of other major normal proteins. Proteins were detected following virus infection which were absent from hemolymph of healthy larvae. These proteins were not serologically related to those present in the virus.

Nuclear polyhedrosis virus-specific soluble antigens in fat body of Trichoplusia ni larvae

Abstract Virus-specific antigens were demonstrated by immunodiffusion in the soluble fraction of fat body in NPV-infected Trichoplusia ni larvae. Four precipitin bands were present on the second day following infection and remained throughout the course of the disease. Two of these bands also were present when the soluble fraction was diffused against polyhedral antiserum. One band coalesced with inclusion body protein. A second band contained at least 2 distinct antigens; one common with inclusion body protein and the other with a virion antigen.

Protein synthesis in fat body of Trichoplusia ni during the course of a nuclear polyhedrosis virus infection

Abstract Protein synthesis in fat body of cabbage looper, Trichoplusia ni , larvae was investigated during the course of a nuclear polyhedrosis virus infection. Fat body total protein concentration increased late in the disease due to a large increase in the saline-insoluble protein fraction. Incorporation of 14 C-leucine into fat body proteins in vitro revealed a slight increase in synthesis of both retained and released proteins on the first day of the disease followed by a rapid decrease in protein synthesis. The rate of decrease was more rapid in released than in retained proteins. Fat body soluble proteins of healthy larvae were separated into 22 bands by disc acrylamide gel electrophoresis. In diseased larvae, the concentration of major protein bands decreased during late stages of the disease. Electropherograms of the soluble fraction following 14 C-leucine incorporation revealed most protein synthesized in the fifth instar of healthy larvae was in 2 zones close to the origin of the gels. These proteins were rapidly released following synthesis and accounted for all but trace amounts of the released protein. Synthesis of these major proteins decreased rapidly in diseased larvae after the first day as did synthesis of released proteins. Radioactivity in other areas of the gels was well maintained in retained proteins of diseased larvae until the fourth day when little radioactivity was present in any area of the gel.