This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Payne, C. C. Articles by Kalmakoff, J. Search for Related Content PubMed PubMed Citation Articles by Payne, C. C. Articles by Kalmakoff, J.

Alkaline Protease Associated with Virus Particles of a Nuclear Polyhedrosis Virus: Assay, Purification, and Properties

C. C. Payne and J. Kalmakoff

¹ Natural Environment Research Council, Unit of Invertebrate Virology, Oxford OX1 3UB, United Kingdom

ABSTRACT

Proteolytic activity was detected within polyhedra of the nuclear polyhedrosis virus of Spodoptera littoralis. The enzyme activity was detected by its ability to degrade the major structural polypeptide of polyhedra (polyhedrin). A quantitative assessment of activity was made by a radioassay technique using ³H-labeled polyhedrin as the substrate. Of the structural components of polyhedra, virus particles showed the greatest specific proteolytic activity. Preparations of purified nucleocapsids were inactive. The virus particle enzyme displayed a temperature optimum for proteolysis of 30 to 40°C and a pH optimum of 9.6. Its activity was inhibited by H²⁺ and Cu²⁺, but not by 2-mercaptoethanol. The enzyme was purified from detergent-treated virus particles by affinity column chromatography, using polyhedrin linked to cyanogen bromide-activated Sepharose. Three major envelope polypeptides (L107, L85, and L71) bound to the column at 4°C, but after incubation at 31°C, polypeptide L71 alone was eluted. The fractions containing this protein exhibited a specific enzyme activity more than 80-fold greater than that present in polyhedra. The possible significance of the alkaline protease, and other proteins with affinity for polyhedrin, is discussed.

Present address: Department of Entomology, Glasshouse Crops Research Institute, Rustington, Littlehampton, West Sussex BN16 3PU, United Kingdom.

Present address: Department of Microbiology, University of Otago, Dunedin, New Zealand.