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PubMedDate not supplied

Structural alteration of viral homologue of receptor proto-oncogene fms at carboxyl terminus.

A role for proto-oncogenes in the regulation and modulation of cell proliferation has been suggested by the findings that the B-chain of platelet-derived growth factor (PDGF) is encoded by the proto-oncogene sis and that the erb-B oncogene product is a truncated form of the epidermal growth factor (EGF) receptor. Furthermore, the product of the proto-oncogene fms (c-fms) may be related or identical to the receptor for macrophage colony-stimulating factor (CSF-1). v-fms is the transforming gene of the McDonough strain of feline sarcoma virus (SM-FeSV) and belongs to the family of src-related oncogenes which have tyrosine-specific kinase activity. Furthermore, nucleotide sequence analysis of the v-fms gene product revealed topological properties of a cell-surface receptor protein. To elucidate the features involved in the conversion of a normal cell-surface receptor gene into an oncogenic one, we have now determined the complete nucleotide sequence of a human c-fms complementary DNA. The 972-amino-acid c-fms protein has an extracellular domain, a membrane-spanning region, and a cytoplasmic tyrosine protein kinase domain. Comparison of the feline v-fms and human c-fms sequences reveals that the proteins share extensive homology but have different carboxyl termini.

Amino Acid Sequence↗
PubMed2006

A vaccinia virus lacking A10L: viral core proteins accumulate on structures derived from the endoplasmic reticulum.

The assembly of the intracellular mature virus (IMV) of vaccinia virus (VV), the prototype member of the poxviridae, is poorly understood and controversial. We have previously proposed that the IMV is composed of a continuous double-membraned cisterna derived from the smooth ER, whereby the genome-containing core is enwrapped by a part of this cisterna. In the present study we characterize a mutant virus in which the synthesis of the major core protein A10L can be conditionally expressed. Without A10L, IMVs are not made; immature viruses (IVs) and regularly stacked membrane structures that contain viral DNA, accumulate instead. By immunolabelling of thawed cryo-sections these stacks contain most of the viral core proteins and low levels of viral membrane proteins. Importantly, the stacked membranes could be labelled with antibodies to an ER marker protein, implying that they are derived from this cellular compartment. By electron tomography (ET) on semi-thin cryo-sections we show that the membranes of the stacks are continuous with the membranes of the IVs. Direct continuities with ER cisternae, to which the stacks are tightly apposed, were, however, not unequivocally seen. Finally, ET revealed how the IV membranes separated to become two-membrane profiles. Taken together, this study shows that VV core proteins and the viral DNA can coassemble onto ER-derived membranes that are continuous with the membranes of the IVs.

Animals↗
PubMed1981

Structure of Sendai viral proteins in plasma membranes of virus-infected cells.

Purified plasma membranes attached to polycationic polyacrylamide beads by their external surface were isolated from BHK cells infected with Sendai virus. Each of the viral proteins could be identified in the membranes of infected cells. Proteolysis with trypsin, which digests only the cytoplasmic surface of these membranes (because the external surface is protected by its attachment to beads), revealed that the internal proteins, L, P, NP, and M, were present on the cytoplasmic surface of the membrane and that small segments of the viral envelope glycoproteins, HN and F0, were partially exposed on the cytoplasmic surface. Since the major portions of HN and F0 are known to be present on the external membrane surface, these glycoproteins are transmembrane proteins before Sendai virus budding in infected cells.

Animals↗
PubMed2004

Characterization of functional hepatitis C virus envelope glycoproteins.

Hepatitis C virus (HCV) encodes two envelope glycoproteins, E1 and E2, that assemble as a noncovalent heterodimer which is mainly retained in the endoplasmic reticulum. Because assembly into particles and secretion from the cell lead to structural changes in viral envelope proteins, characterization of the proteins associated with the virion is necessary in order to better understand how they mature to be functional in virus entry. There is currently no efficient and reliable cell culture system to amplify HCV, and the envelope glycoproteins associated with the virion have therefore not been characterized yet. Recently, infectious pseudotype particles that are assembled by displaying unmodified HCV envelope glycoproteins on retroviral core particles have been successfully generated. Because HCV pseudotype particles contain fully functional envelope glycoproteins, these envelope proteins, or at least a fraction of them, should be in a mature conformation similar to that on the native HCV particles. In this study, we used conformation-dependent monoclonal antibodies to characterize the envelope glycoproteins associated with HCV pseudotype particles. We showed that the functional unit is a noncovalent E1E2 heterodimer containing complex or hybrid type glycans. We did not observe any evidence of maturation by a cellular endoprotease during the transport of these envelope glycoproteins through the secretory pathway. These envelope glycoproteins were recognized by a panel of conformation-dependent monoclonal antibodies as well as by CD81, a molecule involved in HCV entry. The functional envelope glycoproteins associated with HCV pseudotype particles were also shown to be sensitive to low-pH treatment. Such conformational changes are likely necessary to initiate fusion.

Antibodies, Monoclonal↗
PubMedDate not supplied

[The etiological structure of acute viral hepatitis in Tadzhikistan in a period of decreased morbidity].

In the period of reduced incidence of viral hepatitis in Tajikistan, January-December, 1990, 1562 patients with acute viral hepatitis (AVH) were examined in the first days of the jaundice phase (928 children under 14 years and 634 adults) in Dushanbe. Markers of hepatitis A, B, and D (HBsAg, anti-HA IgM, anti-HBc IgM, anti-delta IgM) were determined by enzyme immunoassay. Hepatitis A occurred in 25.8% of the patients with AVH, mostly children of 1-6 years, HB in 22.8%, HD co- and superinfection) in 9.2%. In 42.1% of the patients who had no HA, HB, or HD markers in the blood, non-A, non-B hepatitis (mostly hepatitis E) was diagnosed, mainly in the age groups of 30-39 years (70.7%) and 15-29 years (59.2%). Thus, in Tajikistan hepatitis E occurs not only during outbreaks of this infection but also sporadically.

Acute Disease↗
PubMedDate not supplied

[Antibodies to the structural proteins of the chrysanthemum B-virus in normal human plasma].

Electrophoretic analysis of the protein composition of chrysanthemum B virus (ChrBV), a member of the carlavirus family, performed in 7.5-15% gradient polyacrylamide gel with 0.1% SDS revealed the presence in the preparation of two proteins with molecular weights of 34,000 and 37,000. The densitometric treatment showed their ratio approximating 2:1. Antibodies to these proteins were detected in a pool of normal human plasma and in individual human sera by the immune blotting test. No antibodies to ChrBV proteins were found in goat and rabbit sera. Normal human plasma contained no antibodies to structural proteins of tobacco mosaic, cucumber mosaic, and rock-cress mosaic viruses. It is presumed that the presence of antibody to ChrBV proteins may be associated either with casual structural relationship of viral and some cellular (serum) proteins or with immunization of man with ChrBV or immunologically related carlavirus(es).

Animals↗