Proteins specified by herpes simplex virus. V. Purification and structural proteins of the herpesvirion

Abstract

We are reporting a procedure for the purification of herpes simplex enveloped nucleocapsids (virions), an evaluation of the purification procedure and the results of analyses of the virion proteins by high-resolution acrylamide gel electrophoresis. The data may be summarized as follows. (i) The procedure for the purification of virions consists of careful extraction of cytoplasm to prevent nuclear breakage, separation of enveloped nucleocapsids from soluble proteins and membrane vesicles by rate zonal centrifugation of cytoplasmic extracts through dextran 10 gradients, treatment with urea to dissociate virus-debris aggregates, and, lastly, separation of virions from naked nucleocapsids and free membranes by isopycnic flotation in discontinuous sucrose gradients. (ii) Purity was evaluated in three ways, i.e., electron microscopic examination, analysis of purified virions produced in cells labeled with amino acids before infection, and analysis of purified virions from artificial mixtures of infected and labeled, uninfected cells. The extent of purification was 120-to 200-fold with respect to host proteins. Residual contaminants were identified as host and viral constituents of membrane vesicles. Residual host proteins are very likely contaminants and not structural components of the virion. (iii) Analyses by staining and autoradiography of structural proteins of purified virions in 6, 7, 8.5, 9, and 14% acrylamide gels revealed 24 bands of proteins and glycoproteins made and labeled after infection. Co-electrophoresis of viral proteins with six known standards ranging from 25,700 to 220,000 daltons in molecular weight in 6, 7, 8.5, and 9% acrylamide gels indicate that viral proteins range from 25,000 to 275,000 daltons. The sum of the molecular weights of viral proteins is 2,580,000 daltons. Assuming that messenger transcription is asymmetric and noncomplementary, this corresponds to 47% of the genetic information of the virus. (iv) The nonionic detergent NP-40 removes from purified virions some nonglycosylated proteins and a large fraction of the glycosylated proteins. It leaves behind traces of the envelope visible in the electron microscope as well as some glycoproteins thought to be in the envelope.