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Biomedical subjects

W Garten

Publications and source records attributed to W Garten.

71 records · Page 4Linked to original sources
PubMed1984

The carboxyterminus of the hemagglutinin-neuraminidase of Newcastle disease virus is exposed at the surface of the viral envelope.

The amino-terminal and the carboxy-terminal amino acids of the hemagglutinin-neuraminidase glycoprotein of the Ulster strain of Newcastle disease virus have been analyzed before and after proteolytic activation of the precursor HNo (Mr approximately 82K). The amino termini of HNo and of the large cleavage fragment HN (approximately 74K) obtained by in vivo and in vitro proteolysis could not be sequenced by Edman degradation. This indicates that in both instances the amino termini are blocked. The carboxy termini of HNo and HN are different as demonstrated by end-point digestion with carboxypeptidase A. Furthermore, a small cleavage fragment (approximately 9K) of HNo that was removed from the virion after trypsin treatment could be purified by HPLC. In contrast to HN, this fragment displays a free amino terminus susceptible to Edman degradation. These data indicate that conversion of HNo involves removal of a 9K glycopeptide from the carboxy-terminal end. Thus, it has to be concluded that, unlike most other viral glycoproteins, the hemagglutinin-neuraminidase is inserted in the envelope with its carboxy terminus exposed at the surface of the virus particle.

Amino Acid Sequence↗
PubMed1983

Characterization of the carboxypeptidase involved in the proteolytic cleavage of the influenza haemagglutinin.

The arginine carboxypeptidase involved in the proteolytic cleavage of the haemagglutinin of influenza A virus has been analysed by an assay employing a Sepharose-bound peptide containing radioactive arginine as a substrate. The enzyme activity has been extracted from purified virus with non-ionic detergents and has been separated from the haemagglutinin and from the neuraminidase by isoelectric focusing and by affinity chromatography. The carboxypeptidase present in virus grown in different host cells shows variations in its isoelectric point. It can be concluded from these observations that the carboxypeptidase is a host component incorporated into the virus envelope. When the enzyme is inhibited by 2-mercaptomethyl-3-guanidinoethyl-thiopropanoic acid, haemagglutinin with the arginine attached to the carboxy terminus of HA1 can be obtained. The observation that under these conditions the haemagglutinin has retained its haemolytic activity indicates that the carboxypeptidase does not play an essential role in the activation process.

Carboxypeptidases↗
PubMed1981

The site of cleavage in infected cells and polypeptides of representative paramyxoviruses grown in cultured cells of the chorioallantoic membrane.

Cultured cells of the chorioallantoic membrane (CAM) fulfilled the need of using the same cell system that was permissive for representative paramyxoviruses to carry out studies on the biosynthesis of their glycoproteins in infected cells. The polypeptides composition of the respective paramyxoviruses [Newcastle disease virus (NDV), paramyxovirus Yucaipa (PMY), and Sendai virus], grown in eggs and CAM-cells, was essentially identical. In egg-grown PMY a large glycoprotein (LGP) was present but only in some CAM-grown preparations of virus labeled with [3H]-glucosamine and rarely in [35S]-methionine or [3H]-amino acids (valine, leucine, and tyrosine) labeled viruses. The site of cleavage of precursor F0 to F1,2 was not the same. In contrast to the cleavage of Sendai virus glycoprotein, cleavage was intracellular in NDV and PMY infected cells. Homologous antisera against the glycoproteins failed to inhibit cleavage of HN0 or F0 in cells infected with the representative paramyxoviruses.

Allantois↗
PubMed1980

Mutational changes of the protease susceptibility of glycoprotein F of Newcastle disease virus: effects on pathogenicity.

Two chemically induced mutants with an alteration in the susceptibility of glycoprotein F to proteolytic cleavage have been isolated from the apathogenic strains of La Sota and Ulster of Newcastle disease virus. In contrast to the La Sota wild type, cleavage of the precursor F0 and activation of cell fusing activity and infectivity take place if the mutant is grown in MDBK and BHK21-F cells. The mutant is, therefore, able to undergo multiple replication cycles in cells non-permissive for the wild type. This increase in host range is paralleled by an increase in pathogenicity for chick embryos. The increase in host range of the Ulster mutant is less distinct. This mutant, which does not differ in pathogenicity from its wild type, produces in MDBK cells incompletely activated virus containing predominantly glycoprotein HN in the uncleaved and glycoprotein F in the cleaved form. The data support the concept that the susceptibility of the virus glycoproteins to proteolytic activation is an important factor in determining the pathogenicity of this virus.

Animals↗
PubMed1980

Proteolytic activation of the haemagglutinin-neuraminidase of Newcastle disease virus involves loss of a glycopeptide.

The uncleaved (HN0) and the cleaved (HN) forms of the haemagglutinin-neuraminidase glycoprotein of Newcastle disease virus (NDV), strain Ulster, were analysed by polyacrylamide gel electrophoresis under reducing and non-reducing conditions. When HN0 is converted into HN, a glycopeptide with an apparent mol. wt. of about 8000, which is not found in the mature spike, is removed.

Glycopeptides↗
PubMed1975

The major proteins of the Escherichia coli outer cell-envelope membrane. Cyanogen bromide fragments of protein I, composition and order.

The cyanogen bromide fragments of protein I, a major protein of the Escherichia coli outer cell envelope membrane, have been isolated and characterized. There appear to be two methionine-serine or methionine-threonine sequences causing incomplete cleavage but complete conversion of methionine to homoserine. Largely due to the existence of these overlapping fragments the order of 5 of the 6 fragments present could be deduced. None of the fragments exhibits any remarkable low degree of polarity, and the tryptic fingerprint of the largest fragment (comprising about 60% of protein I) also does not show any conspicuous large fraction of lipophilic peptides. It is concluded that the domain of protein I that may be buried in the lipid phase of the outer membrane in all likelihood is not very large, and there is, in fact, no definite proof yet that protein I is a membrane protein sensu stricto.

Amino Acid Sequence↗
PubMed1975

The major proteins of the Escherichia coli outer cell envelope membrane. Characterization of proteins II* and III, comparison of all proteins.

Protein II*, one of the major Escherichia coli outer cell envelope membrane proteins has been characterized. The protein is heat-modifiable and perhaps due to complete unfolding and/or binding of sodium dodecylsulfate only at higher temperatures the modified protein exhibits a higher apparent molecular weight (33,000) than the non-modified form (28,000). Protein-chemical evidence as well as the behavior of two mutant proteins II* very strongly suggest that this protein consists of a single polypeptide chain and that in the strains studied there is no other major protein with similar characteristics. For another outer membrane protein, protein III (molecular weight 17,000), it has not yet been established if it should be classified as a major protein. Protein III consists of one or perhaps two polypeptide chains. The possibility existed that protein III is bound covalently to lipopolysaccharide, and this has been ruled out. Also, the lipopolysaccharide of the E. coli strains studied does not carry covalently bound protein in amounts anywhere near stoichiometry. N-on-protein substituents were neither found in protein II* nor in protein III. It is concluded that in E. coli B/r and the E. coli K12 strains used there are three major proteins: I, II, and IV; protein III may also belong to this class. There are not more major proteins than these. All four proteins are compared and discussed regarding their unknown functions and their relation to E. coli outer membrane proteins studied by other authors.

Amino Acids↗
PubMedDate not supplied

[Characterization of proteolytic cleavage of influenza virus nucleocapsid protein NP in infected cells].

Antibodies specific to the N-terminal 34-aminoacid peptide of the major nucleocapsid protein NP of human influenza A viruses were obtained. The NP proteolytic cleavage occurring in infected cells late in infection has been demonstrated using this antibody. The antibody specifically reacted with noncleaved NP of 56 kD m.w. but not with cleaved NP of 53 kD m.w. This indicates that NP56-->NP53 intracellular cleavage released the N-terminal 3 kD peptide of Np molecule. The released 3 kD peptide did not accumulate in infected cells. Since the RNA-binding and nucleus migrating signals are located in the N-terminus of NP molecule, presumably, the terminal cleavage is important for intracellular NP functions.

Animals↗