Search results for "virus"
showing 10 items of 5024 documents
Deoxyribonucleases in Herpes simplex Virus Type 1 and 2 Infected Primary Rabbit Kidney Cells
1980
Abstract In primary rabbit kidney cells infected with herpes simplex virus four different neutral deoxyribonuclease activities can be detected by means of the deoxyribonuclease assay in DNA-containing polyacrylamide gels following their separation by discelectrophoresis. The method is suitable to follow independently the change in each activity of the different enzymes using only about 5 × 105 cells for each assay during the time-course of infection. Under these conditions one enzyme activity is constant, two disappear while the activity of a fourth one present only in infected cells, increases.
Thermodynamics of the interaction between the spike protein of severe acute respiratory syndrome- coronavirus-2 and the receptor of human angiotensin…
2020
Since the end of 2019, the coronavirus SARS-CoV-2 has caused more than 180,000 deaths all over the world, still lacking a medical treatment despite the concerns of the whole scientific community. Human Angiotensin-Converting Enzyme 2 (ACE2) was recently recognized as the transmembrane protein serving as SARS-CoV-2 entry point into cells, thus constituting the first biomolecular event leading to COVID-19 disease. Here, by means of a state-of-the-art computational approach, we propose a rational evaluation of the molecular mechanisms behind the formation of the complex and of the effects of possible ligands. Moreover, binding free energy between ACE2 and the active Receptor Binding Domain (RB…
Large-scale analysis of SARS-CoV-2 spike-glycoprotein mutants demonstrates the need for continuous screening of virus isolates
2021
AbstractDue to the widespread of the COVID-19 pandemic, the SARS-CoV-2 genome is evolving in diverse human populations. Several studies already reported different strains and an increase in the mutation rate. Particularly, mutations in SARS-CoV-2 spike-glycoprotein are of great interest as it mediates infection in human and recently approved mRNA vaccines are designed to induce immune responses against it.We analyzed 146,917 SARS-CoV-2 genome assemblies and 2,393 NGS datasets from GISAID, NCBI Virus and NCBI SRA archives focusing on non-synonymous mutations in the spike protein.Only around 13.8% of the samples contained the wild-type spike protein with no variation from the reference. Among…
Deletion and insertion mutants of HBsAg particles
1992
We have found previously that hybrid 22-nm HBsAg particles can be created by insertion of short antigenic sequences into the HBV major envelope protein [1]. We have now performed a detailed deletion mutagenesis of the S gene of HBV encoding HBsAg. Deletion of the 51 C-terminal amino acids including most of the third and all of the fourth hydrophobic domain of the S protein did not affect particle assembly and secretion. However, secretion of 22-nm particles was abolished by minor deletions in the N-terminal region. Insertion and deletion/substitution mutants carrying a poliovirus epitope at the N-terminus and the preSl region at the C-terminus have been characterized.
Biochemical and Kinetic Analyses of NS5B RNA-Dependent RNA Polymerase of the Hepatitis C Virus
1998
The biochemical properties of the RNA-dependent RNA polymerase (RdRp) of the hepatitis C virus were analyzed. A hexahistidine affinity-tagged NS5B fusion protein was expressed with recombinant baculoviruses in insect cells and purified to near homogeneity. Enzymatic activity of the purified protein was inhibited by KCl or high concentrations of NaCl and was absolutely dependent on Mg2+, which could be replaced by Mn2+. NS5B was found to be processive and able to copy long heteropolymeric templates with an elongation rate of 150-200 nucleotides/min at 22 degreesC. Kinetic constants were determined for all four nucleoside triphosphates and different templates. In case of a heteropolymeric RNA…
Proteins of Human Cytomegalovirus that Elicit Humoral Immunity
1993
Several of the cytomegalovirus (CMV) genes encoding glycoproteins, structural proteins, and infected-cell proteins that elicit an immune response in human infection have been mapped. Human sera and monoclonal antibodies react with these viral polypeptides made as native molecules in CMV-infected cells, as genetically engineered proteins, as truncated derivatives expressed in eukaryotic cells, and as bacterial fusion proteins from portions of the reading frames cloned into prokaryotic expression vectors. Synthetic oligopeptides from immunodominant regions of these molecules have also been used as antibody targets. Studies on proteins encoded by reading frames UL55, UL32, and UL44, on glycopr…
FORMATION OF A SMALL RIBONUCLEOPROTEIN PARTICLE BETWEEN TAT PROTEIN AND TRANS-ACTING RESPONSE ELEMENT IN HUMAN IMMUNODEFICIENCY VIRUS-INFECTED CELLS
1991
The trans-acting response element (TAR) within the long terminal repeat of human immunodeficiency virus (HIV) is present in all 5' termini of HIV mRNAs and is recognized by the viral Tat protein. Now we describe that the 59-nucleotide-long TAR-RNA exists as a ribonucleoprotein particle in polysomal and heterogeneous nuclear RNP fractions of HIV-1-infected HeLa-T4+ cells. Applying an immunoprecipitation technique this Tat.TAR complex could be isolated from total cell extracts as well as from polysomal or heterogeneous nuclear RNP fractions. The chain length and the identity of the TAR-RNA were established by RNase protection assays while the Tat protein was confirmed by Western blotting tech…
Inhibition of herpesvirus DNA synthesis by 9-beta-D-arabinofuranosyladenine in cellular and cell-free systems.
1977
9-beta-D-Arabinofuranosyladenine 5'-triphosphate (ara-ATP) is an inhibitor both of DNA polymerase-alpha and -beta from noninfected rabbit kidney cells and of the DNA-dependent DNA polymerase induced by herpes simplex virus Type 1 (strain IES). The studies were performed with partially purified enzymes, and each of the different polymerase preparations contained only one DNA-dependent DNA polymerase species. These enzymes were inhibited in a competitive manner. The HSV-induced DNA-dependent DNA polymerase was 39-fold more sensitive to ara-ATP than was cellular DNA polymerase-beta and 116-fold more sensitive than cellular DNA polymerase-alpha. The affinity of the HSV-induced enzyme for ara-AT…
Mechanism of the Antiretroviral Effect of dsRNA
1994
The development of AIDS seems to be linked to an impairment of processes which are induced or activated by double-stranded RNA (dsRNA), such as the biosynthesis of interferon (IFN), production of 2′,5′-oligoadenylate (2-5A), ribonuclease L (RNase L) activity and different cell-mediated immune functions. A restriction of available bioactive dsRNA (or of dsRNA-dependent enzymes) may play an important role in the disease progression. The results summarized in this review show that defects in dsRNA-dependent pathways exhibited by AIDS patients can be reversed, at least in part, by exogenously supplied dsRNA.
Saponins as immunoadjuvants and immunostimulants
1999
Saponins are either triterpene or steroid glycosides widely distributed in the plant and animal kingdom and include a large number of biologically active compounds. Most of them have surface-active and cholesterol-binding properties.