Enzymatic radioiodination of the envelope proteins of avian myeloblastosis virus

Development of cerebellar cells in neuron-enriched cultures: cell surface proteins

Lactoperoxidase catalyzed 125I-iodination of 8-day-old rat cerebellar cultures enriched in interneurons, mainly granule cells, was studied during a period 1-8 days in vitro, when the mature appearance of the cultures develop. Autoradiography of the surface iodinated constituents after separation by SDS-polyacrylamide gel electrophoresis showed a limited number of heavily labeled bands, including polypeptides of apparent molecular weight (X 10(3] of 140, 88, 68, 58 and 53 daltons. Their relative proportion in terms of 125I-content changed during the development of the cultures. Initially, the labeled 140 kdaltons band (P140) was dominant. Using crossed immunoelectrophoresis with an antiserum raised against immature rat cerebellar plasma membrane preparations (anti-BPM serum) that primarily recognizes one neuronal surface antigen (D2)33, it was established that the P140 comprises the D2 protein. In contrast to the amount of D2, which increases during the 8-day culture period, the labeling of P140 decreased sharply after 2 DIV. This decline coincided with a developmental change in the molecular forms of D2 involving desialylation. Treatment of 2 DIV cultures with neuraminidase, which reproduces the D2 developmental change, prior to 125I-iodination resulted in a marked reduction in the labeling of P140, whereas the other major labeled group of polypeptides in the 50 kdalton range were little affected. Further experiments showed that the D2 protein is phosphorylated in the plasma membrane. It was found that some of the surface labeled proteins, including P140, are released into the culture medium, but apparently in a non-phosphorylated form. Thus it would appear that a significant part of the polypeptide chain of D2, which is an integral membrane constituent, is exposed on the cell surface, and that either D2 has an anchorage within the membrane that is phosphorylated but is not released or D2 is rapidly dephosphorylated when it is shed from the membrane.

Proteins of Epstein-Barr Virus. II. Electrophoretic analysis of the polypeptides of the nucleocapsid and the glucosamine- and polysaccharide-containing components of enveloped virus

Two series of experiments were undertaken to identify the topological location of the structural polypeptides of Epstein-Barr virus. In the first series of experiments, nucleocapsids prepared by detergent treatment of enveloped virus with Nonidet P-40 and sodium deoxycholate were found to be composed of seven polypeptides, VP2, 6, 7.5, 24, 27, 31, ANd 33, which ranged in molecular weight from over 200 X 10(3) to 28 X 10(3). Nine other polypeptides, VP 4, 7, 8, 10, 15, 16, 23, 28, and 29, could be identified in preparations of Epstein-Barr virus nucleocapsids, but the relative amount of this second group of polypeptides was less in preparations of nucleocapsids than in preparations of enveloped virus. The incomplete removal of these polypeptides from enveloped virus by detergent treatment suggests that some of these polypeptides may be components of the envelope or tegument that lie in close proximity to the outer surface of the nucleocapsid In the second series of experiments periodic acid-Schiff-staining and glucosamine-containing components were identified with similar electrophoretic mobility to several of the polypeptides of enveloped virus (VP 5, 8, 9, 11, 12, 13, 14, 15, 16, 17, 28, and 29) that were completely or incompletely removed from purified virus preparations by detergent treatment. The similarity between the polypeptide composition of the nucleocapsids of Epstein-Barr virus and herpes simplex virus was in contrast to the dissimilarity between the nonnucleocapsid polypeptides of Epstein-Barr virus and herpes simplex virus.

In vitro radiolabeling procedure which labels the proteins of Newcastle disease virions with carbon-14

A convenient and gentle procedure was used for in vitro radioisotopic labeling the proteins of Newcastle disease virus. This method, which utilizes [14C]formaldehyde and sodium borohydride, labels all the proteins of purified Newcastle disease virus. Virions labeled in this manner retained biological and biopysical integrity

In vitro radioisotopic labeling of proteins associated with purified polyoma virions

An in vitro procedure using [(14)C]formaldehyde and sodium borohydride was used to label the proteins of purified polyoma virions. This method, which labeled the three capsid proteins and the four internal histones of polyoma virus, did not alter the biological and biophysical characteristics of the virus. In addition to the seven viral proteins, five additional radioactive peaks were resolved on polyacrylamide gels. Four of these peaks could be attributed to growing the virus in the presence of serum. The fifth peak appears to be a nonhistone host-contributed protein made before infection.

Structure of the mouse mammary tumor virus: characterization of bald particles

The polypeptide, antigenic, and morphological structure of the mouse mammary tumor virus was studied following protease digestion of intact virions. Intact, untreated virions (rho = 1.17 g/ml) had characteristic envelope spikes, five major polypeptides, and were precipitated by antisera against gp52. Two of the major polypeptides, with molecular weights of 52,000 (gp52) and 36,000 (gp36), had carbohydrate moieties. Protease treatment resulted in spikeless, "bald" particles (rho = 1.14 g/ml), which had altered surface antigenicity and which contained neither gp52 nor gp36. These data indicated that gp52 and gp36 were on the viral envelope. Bald particles retained a 28,000 dalton polypeptide (p28) which was proposed as the major internal polypeptide.