Which are the 6 steps involved in protein synthesis?

04/09/2016 · What enzymes are involved in protein synthesis

proteins involved in the protein synthesis machinery ..

N2 - Hepatitis C virus (HCV) NS3 is a multifunctional protein composed of a protease domain and a helicase domain linked by a flexible linker. Protease activity is required to generate viral nonstructural (NS) proteins involved in RNA replication. Helicase activity is required for RNA replication, and genetic evidence implicates the helicase domain in virus assembly. Binding of protease inhibitors (PIs) to the protease active site blocks NS3-dependent polyprotein processing but might impact other steps of the virus life cycle. Kinetic analyses of antiviral suppression of cell culture-infectious genotype 1a strain H77S.3 were performed using assays that measure different readouts of the viral life cycle. In addition to the active-site PI telaprevir, we examined an allosteric protease-helicase inhibitor (APHI) that binds a site in the interdomain interface. By measuring nucleotide incorporation into HCV genomes, we found that telaprevir inhibits RNA synthesis as early as 12 h at high but clinically relevant concentrations. Immunoblot analyses showed that NS5B abundance was not reduced until after 12 h, suggesting that telaprevir exerts a direct effect on RNA synthesis. In contrast, the APHI could partially inhibit RNA synthesis, suggesting that the allosteric site is not always available during RNA synthesis. The APHI and active-site PI were both able to block virus assembly soon (

does protein sythesis use the enzyme helicase? | Yahoo …

AB - The coronavirus mouse hepatitis virus (MHV) translates its replicase gene (gene 1) into two co-amino-terminal polyproteins, polyprotein 1a and polyprotein lab. The gene 1 polyproteins are processed by viral proteinases to yield at least 15 mature products, including a putative RNA helicase from polyprotein lab that is presumed to be involved in viral RNA synthesis. Antibodies directed against polypeptides encoded by open reading frame lb were used to characterize the expression and processing of the MHV helicase and to define the relationship of helicase to the viral nucleocapsid protein (N) and to sites of viral RNA synthesis in MHV-infected cells. The antihelicase antibodies detected a 67-kDa protein in MHV-infected cells that was translated and processed throughout the virus life cycle. Processing of the 67-kDa helicase from polyprotein lab was abolished by E64d, a known inhibitor of the MHV 3C-like proteinase. When infected cells were probed for helicase by immunofluorescence laser confocal microscopy, the protein was detected in patterns that varied from punctate perinuclear complexes to large structures that occupied much of the cell cytoplasm. Dual-labeling studies of infected cells for helicase and bromo-UTP-labeled RNA demonstrated that the vast majority of helicase-containing complexes were active in viral RNA synthesis. Dual-labeling studies for helicase and the MHV N protein showed that the two proteins almost completely colocalized, indicating that N was associated with the helicase-containing complexes. This study demonstrates that the putative RNA helicase is closely associated with MHV RNA synthesis and suggests that complexes containing helicase, N, and new viral RNA are the viral replication complexes.

Hepatitis C virus (HCV) NS3 is a multifunctional protein composed of a protease domain and a helicase domain linked by a flexible linker. Protease activity is required to generate viral nonstructural (NS) proteins involved in RNA replication. Helicase activity is required for RNA replication, and genetic evidence implicates the helicase domain in virus assembly. Binding of protease inhibitors (PIs) to the protease active site blocks NS3-dependent polyprotein processing but might impact other steps of the virus life cycle. Kinetic analyses of antiviral suppression of cell culture-infectious genotype 1a strain H77S.3 were performed using assays that measure different readouts of the viral life cycle. In addition to the active-site PI telaprevir, we examined an allosteric protease-helicase inhibitor (APHI) that binds a site in the interdomain interface. By measuring nucleotide incorporation into HCV genomes, we found that telaprevir inhibits RNA synthesis as early as 12 h at high but clinically relevant concentrations. Immunoblot analyses showed that NS5B abundance was not reduced until after 12 h, suggesting that telaprevir exerts a direct effect on RNA synthesis. In contrast, the APHI could partially inhibit RNA synthesis, suggesting that the allosteric site is not always available during RNA synthesis. The APHI and active-site PI were both able to block virus assembly soon (


Start studying PCB DNA Replication - Proteins Involved Part 1 ..

The ATP-dependent DNA helicase RecQ () is involved in genome maintenance []. All homologues tested to date unwind paired DNA, translocating in a 3' to 5' direction and several have a preference for forked or 4-way DNA structures (e.g. Holliday junctions) or for G-quartet DNA. The yeast protein, Sgs1, is present in numerous foci that coincide with sites of synthesis DNA, such as the replication fork, and protein levels peak during S-phase.

Function in DNA replication; DNA Helicase: ..

A model has been proposed for Sgs1p action in the S-phase checkpoint response, both as a 'sensor' for damage during replication and a 'resolvase' for structures that arise at paused forks, such as the four-way 'chickenfoot' structure. The action of Sgs1p may serve to maintain the proper amount and integrity of ss DNA that isnecessary for the binding of RPA (replication protein A, the eukaryotic ss DNA-binding protein)-DNA pol complexes. Sgs1p would thus function by detecting (or resolving) aberrant DNA structures, and would thuscontribute to the full activation of the DNA-dependent protein kinase, Mec1p and the effector kinase, Rad53p. Its ability to bind both the large subunit of RPA and theRecA-like protein Rad51p, place it in a unique position to resolve inappropriate fork structures that can occur when either the leading or lagging strandsynthesis is stalled. Thus, RecQ helicases integrate checkpoint activation and checkpoint response.