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V M Vogt

Publications and source records attributed to V M Vogt.

At least 73 records · Page 4Linked to original sources
PubMed1983

H protein, a minor protein of TMV virions, contains sequences of the viral coat protein.

H protein, a minor protein found associated with virions of tobacco mosaic virus (TMV) at an average of about one copy per virion and previously believed to be host-coded (Asselin and Zaitlin, 1978, Virology 91, 173-181), has been shown to contain sequences of the viral capsid protein. Two-dimensional tryptic peptide maps of 125I-labeled H protein (Mr 26,500) and coat protein (Mr 17,500) from TMV strains U1 and Dahlemense show that the respective H proteins contain most if not all of the labeled peptides of the coat proteins in addition to 2-3 unique peptides. The H proteins also contain unique antigenic determinants, as antibodies can be isolated which react strongly with the H protein but not with the coat protein of Dahlemense TMV. Finally, amino acid composition analysis of the U1-TMV H protein has shown the presence of methionine and histidine, amino acids not present in the coat protein of that strain. H protein appears to contain the same NH2 terminus as coat protein, as there is an H protein tryptic peptide that both comigrates in a two-dimensional system and produces the same acid cleavage product as the NH2-terminal tryptic peptide of coat protein. H protein also seems to have the same COOH terminus as coat protein, as cyanogen bromide digestion of Dahlemense-TMV coat protein and H protein indicates that each has a methionine about 12 amino acids from one terminus (known to be the COOH terminus of the coat protein). Thus, H protein is not structurally equivalent to coat protein with an addition on either its NH2 or COOH terminus. However, H protein does not appear to be a noncovalent aggregate of coat protein and some other protein. Rather, the model we favor for H protein structure is that of a branched fusion product between coat protein and another polypeptide of host or viral origin.

Capsid Proteins↗
PubMed1983

Purification and properties of a fifth major viral gag protein from avian sarcoma and leukemia viruses.

We have developed procedures for the purification of a 6,000-dalton protein from avian myeloblastosis virus. This protein is a major component of avian myeloblastosis virus, accounting for over 7% of total protein, and thus is equimolar with the other internal structural proteins in virions. As described in the accompanying paper (Hunter et al., J. Virol. 45:885-888, 1983), the results of N-terminal amino acid sequence analysis identify the protein as a product of the gag gene. We suggest denoting this protein as p10, according to nomenclature that is already in use for a previously identified but poorly defined low-molecular-weight protein or proteins of avian sarcoma and leukemia viruses. In virions p10 appears to be located between the core and the membrane. Several of its properties may explain why p10 has not been characterized previously. Among these are its abnormal amino acid composition, its solubility under conditions where most proteins are fixed into sodium dodecyl sulfate-polyacrylamide gels, and the variability in its electrophoretic migration in different avian sarcoma viruses.

Alpharetrovirus↗
PubMed1983

Amino-terminal amino acid sequence of p10, the fifth major gag polypeptide of avian sarcoma and leukemia viruses.

We have identified p10 as a fifth gag protein of avian sarcoma and leukemia viruses. Amino-terminal protein sequencing of this polypeptide purified from the Prague C strain of Rous sarcoma virus and from avian myeloblastosis virus implies that it is encoded within a stretch of 64 amino acid residues between p19 and p27 on the gag precursor polypeptide. For p10 from the Prague C strain of Rous sarcoma virus the first 30 residues were found to be identical with the predicted amino acid sequence from the Prague C strain of Rous sarcoma virus DNA sequence, whereas for p10 from avian myeloblastosis virus the protein sequence for the same region showed two amino acid substitutions. Amino acid composition data indicate that there are no gross composition changes beyond the region sequenced. The amino terminus of p10 is located two amino acid residues past the carboxy terminus of p19, whereas its carboxy terminus probably is located immediately adjacent to the first amino acid residue of p27.

Amino Acid Sequence↗
PubMed1983

Inheritance of extrachromosomal rDNA in Physarum polycephalum.

In the acellular slime mold Physarum polycephalum, the several hundred genes coding for rRNA are located on linear extrachromosomal DNA molecules of a discrete size, 60 kilobases. Each molecule contains two genes that are arranged in a palindromic fashion and separated by a central spacer region. We investigated how rDNA is inherited after meiosis. Two Physarum amoebal strains, each with an rDNA recognizable by its restriction endonuclease cleavage pattern, were mated, the resulting diploid plasmodium was induced to sporulate, and haploid progeny clones were isolated from the germinated spores. The type of rDNA in each was analyzed by blotting hybridization, with cloned rDNA sequences used as probes. This analysis showed that rDNA was inherited in an all-or-nothing fashion; that is, progeny clones contained one or the other parental rDNA type, but not both. However, the rDNA did not segregate in a simple Mendelian way; one rDNA type was inherited more frequently than the other. The same rDNA type was also in excess in the diploid plasmodium before meiosis, and the relative proportions of the two rDNAs changed after continued plasmodial growth. The proportion of the two rDNA types in the population of progeny clones reflected the proportion in the parent plasmodium before meoisis. The rDNAs in many of the progeny clones contained specific deletions of some of the inverted repeat sequences at the central palindromic symmetry axis. To explain the pattern of inheritance of Physarum rDNA, we postulate that a single copy of rDNA is inserted into each spore or is selectively replicated after meiosis.

Extrachromosomal Inheritance↗
PubMed1982

Avian sarcoma virus gag precursor polypeptide is not processed in mammalian cells.

We studied intracellular avian gag proteins (internal structural proteins of virions) in several mammalian cell lines transformed by Rous sarcoma virus. All lines examined contain gag antigens as determined by radioimmune assay. We used the techniques of protein blotting from polyacrylamide gels, which detects nanogram quantities of viral protein, to investigate the size of intracellular viral polypeptides. All of the lines that contained enough viral protein to be amenable to this type of analysis synthesized Pr76, the avian sarcoma virus gag precursor polypeptide, but failed to process it into mature virion proteins. In some cell lines, the recovery of Pr76 was greatly enhanced by the addition of a mixture of protease inhibitors, including the sulfhydryl-blocking reagent N-ethylmaleimide, to the lysis buffer. At least several of the mammalian cells also synthesized a viral polypeptide the size of Pr180, the precursor to reverse transcriptase. Since Rous sarcoma virus does not replicate or replicates extremely poorly in mammalian cells, the lack of processing suggests that cleavage and virion assembly are invariably associated.

Animals↗
PubMed1982

Accessibility of ribosomal genes to trimethyl psoralen in nuclei of Physarum polycephalum.

We have probed the accessibility of the genes for rRNA in Physarum polycephalum by using the photoreactive DNA cross-linking agent 4,5',8-trimethyl psoralen. Nuclei isolated from actively growing Physarum were treated with trimethyl psoralen and irradiated with 360-nm light in order to form cross-links. The palindromic, extrachromosomal rDNA then was isolated, and the positions of cross-links were determined by electron microscopy of the DNA under totally denaturing conditions. The results indicate that the frequency of cross-linking, after correction for base sequence bias of the reaction, is up to sixfold higher in the transcribed regions than in the central or the terminal spacer regions. There is no detectable heterogeneity among the different rDNA molecules or between the halves of a single molecule. Cross-linked molecules invariably occur in a linear as opposed to a cruciform structure. The preferential cross-linking of the transcribed region is nearly eliminated in spherules, a dormant transcriptionally inactive form in the Physarum life cycle.

Base Sequence↗
PubMed1981

A mouse homolog to the avian sarcoma virus src protein is a member of a protein kinase cascade.

Recent work has identified a cascade of membrane bound protein kinases in Ehrlich ascites tumor cells. These enzymes, designated PKL, PKS and PKM, are present in both Ehrlich tumor and mouse brain, but the cascade is active only in the tumor tissue. We have now purified a fourth protein kinase, PKF, that is also associated with this cascade. Protein kinase F prosphorylates PKL and is phosphorylated by PKS. The position of this kinase in the cascade is as follows, where the arrows denote phosphorylation: [Formula: see text] The phosphorylation by PKF, like phosphorylation by the other kinases, is at a tyrosine residue and causes the substrate kinase (PKL) to become active. The role of the tyrosine phosphorylation in activating these kinases is described in detail elsewhere. One result of activation of the cascade is the phosphorylation of the beta subunit of the Na+K+-ATPase, which causes inefficient Na+ pumping and is at last in part responsible for the high aerobic glycolysis of Ehrlich ascites tumor cells. By several criteria protein kinase F from Ehrlich cells is homologous to the src gene product (pp60src) from avian sarcoma viruses. Antiserum raised against PKF and sera from rabbits bearing rous sarcoma virus (RSV)-induced tumors quantitatively precipitate the same 60 kd phosphoprotein from cell lysates of three different RSV-transformed cell lines. Both proteins phosphorylate PKL and a 130 kd cytoskeletal protein (vinculin). The tryptic maps of these proteins are closely similar. Both proteins bind specifically to PKL covalently coupled to Sepharose. We used this latter observation to facilitate the purification of pp60 src from RSV-transformed cells.

Amino Acids↗
PubMed1978

The biosynthesis of oncovirus proteins.

The patterns of oncovirus protein biosynthesis are essentially similar for avian and mammalian viruses. In each case the four major internal structural proteins are synthesized as a precursor polypeptide of about 75 000 daltons, the product of the gag gene. Translation occurs on genome-sized mRNA. This polyprotein is cleaved in a series of steps to give the mature proteins. The mechanism and localization of cleavage have not yet been clarified. Viral reverse transcriptase, the product of the pol gene, also is translated on genome-sized mRNA as a precursor, which is a "read-through" product of the neighbouring gag gene. The two major envelope proteins are translated as a glycosylated precursor of apparent molecular weight about 90 000 from the env gene located on a sub-genomic RNA species. The precursor is transported to the plasma membrane where it may mark the site of virus budding. It is cleaved in transport or on the membrane, but the resulting two mature envelope proteins remain tied by disulfide bonds. Sarc, the protein product of the src gene that is responsible for transformation, is translated from a different viral mRNA than the structural proteins. Sarc has not been definitively characterized in any system.

Alpharetrovirus↗
PubMed1977

The replication of ribosomal DNA in Physarum polycephalum.

The DNA coding for ribosomal RNA in Physarum polycephalum exists as a collection of extra-chromosomal molecules of molecular weight 37 X 10(6). We have investigated the replication of rDNA, with the following results. (a) Replication of rDNA is unscheduled. This means that molecules that are replicated at any particular time in one mitotic cycle have an equal probability of replicating again in each time interval in the subsequent cycle. Similarly, in a single cycle, some molecules replicate more than once, and some not at all. (b) Replication forks appear to move bidirectionally from points 45% or 33% from one end of the DNA. Replicating molecules observed by electron microscopy are all linear.

DNA Replication↗