Search results for "recte"
showing 10 items of 463 documents
Curved Edge Routing
2001
We consider the problem of drawing a graph where edges are represented by smooth curves between the associated nodes. Previously curved edges were drawn as splines defined by carefully calculated control points. We present a completely different approach where finding an edge is reduced to solving a differential equation. This approach allows to represent the graph drawing aesthetics directly, even the most complex ones denoting the dependencies among the paths.
Translation of hepatitis B virus (HBV) surface proteins from the HBV pregenome and precore RNAs in Semliki Forest virus-driven expression.
2004
Hepatitis B virus (HBV) pregenome RNA (pgRNA) serves as a translation template for the HBV core (HBc) protein and viral polymerase (Pol). HBV precore RNA (pcRNA) directs the synthesis of the precore (preC) protein, a precursor of the hepatitis B e antigen (HBeAg). pgRNA and pcRNA were expressed in the Semliki Forest virus (SFV) expression system. Besides the HBc and preC proteins, there was revealed the synthesis of all three forms of HBV surface (HBs) proteins: long (LHBs), middle (MHBs) and short (SHBs), the start codons of which are located more than 1000 nt downstream of the HBc and preC start codons. Moreover, other HBV templates, such as 3′-truncated pgRNA lacking 3′ direct repeat and…
Mutational analysis of the cysteine residues in the hepatitis B virus small envelope protein.
1993
The small envelope protein of hepatitis B virus is the major component of the viral coat and is also secreted from cells as a 20-nm subviral particle, even in the absence of other viral proteins. Such empty envelope particles are composed of approximately 100 copies of this polypeptide and host-derived lipids and are stabilized by extensive intermolecular disulfide cross-linking. To study the contribution of disulfide bonds to assembly and secretion of the viral envelope, single and multiple mutants involving all 14 cysteines in HepG2 and COS-7 cells were analyzed. Of the six cysteines located outside the region carrying the surface antigen, Cys-48, Cys-65, and Cys-69 were each found to be …
Sequence-Specific Repression of Cotranslational Translocation of the Hepatitis B Virus Envelope Proteins Coincides with Binding of Heat Shock Protein…
1997
AbstractThe large L envelope protein of the hepatitis B virus has the peculiar capacity to adopt two transmembrane topologies. The N-terminal preS domain of L initially remains in the cytosol while the S domain is cotranslationally inserted into the endoplasmic reticulum membrane. The preS region of about half of the L molecules is posttranslationally translocated to the lumenal space. We now demonstrate that the repression of cotranslational translocation of preS is conferred by a preS1-specific sequence. By analysis of L deletion mutants, the cytosolic anchorage determinant was mapped to amino acid sequence 70 to 94 of L. The intrinsic potential of this determinant to suppress cotranslati…
Deletions in the hepatitis B virus small envelope protein: effect on assembly and secretion of surface antigen particles
1992
The small envelope S protein of hepatitis B virus carrying the surface antigen has the unique property of mobilizing cellular lipids into empty envelope particles which are secreted from mammalian cells. We studied the biogenesis of such particles using site-directed mutagenesis. In this study, we describe the effect of deletions in the N-terminal hydrophobic and hydrophilic domains of the S protein. Whereas short overlapping deletions of hydrophilic sequences flanking the first hydrophobic domain were tolerated, larger deletions of the same sequences were not. Conversely, the hydrophilic region preceding the second hydrophobic domain was not permissive for even short deletions. Deletion of…
Hepatitis B virus assembly is sensitive to changes in the cytosolic S loop of the envelope proteins.
2000
Among the three related L, M, and S envelope proteins of the hepatitis B virus (HBV), the L and S polypeptides are required for virion production. Whereas the pivotal function of the pre-S region of L in nucleocapsid envelopment has been established, the contribution of its S domain and the S protein is less clear. In this study, we evaluated the role of the cytosolic S loop, common to L and S, in HBV assembly by performing mutagenesis experiments. To distinguish between the effect of the mutations on either envelope or virion formation, we investigated the ability of the mutants to assemble into secretable subviral empty envelopes and to replace the wild-type proteins in virion maturation,…
The role of histones and their modifications in the informative content of chromatin
1993
It is traditionally accepted that the DNA sequence cannot by itself explain all the mechanisms necessary for the development of living beings, especially in eukaryotes. Indeed part of the information used in these processes is stored in other ways, generally called ‘epigenetic’, whose molecular mechanisms are mostly unknown. The ultimate explanation for them might reside in the non-DNA moiety of chromatin which may play an active role in heredity (‘chromatin information’). Histones are the universal structural component of chromatin. However, recent studies strongly suggest that histones, and their modifications — especially the reversible acetylation of lysines — may act as a recognition s…
Amino acid substitutions enhancing thermostability of Bacillus polymyxa beta-glucosidase A
1996
Mutations enhancing the thermostability of β-glucosidase A of Bacillus polymyxa, a family 1 glycosyl hydrolase, have been obtained after hydroxylamine mutagenesis of a plasmid containing the bglA gene, transformation of Escherichia coli with the mutagenized plasmid, and identification of transformant colonies that showed β-glucosidase activity after a thermal treatment that inactivated the wild-type enzyme. Two additive mutations have been characterized that cause replacement of glutamate at position 96 by lysine and of methionine at position 416 by isoleucine respectively. The thermoresistant mutant enzymes showed increased resistance to other denaturing agents, such as pH and urea, while …
Exploring the atomic structure of 1.8 nm monolayer-protected gold clusters with aberration-corrected STEM
2017
Abstract Monolayer-protected (MP) Au clusters present attractive quantum systems with a range of potential applications e.g. in catalysis. Knowledge of the atomic structure is needed to obtain a full understanding of their intriguing physical and chemical properties. Here we employed aberration-corrected scanning transmission electron microscopy (ac-STEM), combined with multislice simulations, to make a round-robin investigation of the atomic structure of chemically synthesised clusters with nominal composition Au 144 (SCH 2 CH 2 Ph) 60 provided by two different research groups. The MP Au clusters were “weighed” by the atom counting method, based on their integrated intensities in the high …
Mutilation of RNA phage Qβ virus-like particles: from icosahedrons to rods
2000
Icosahedral virus-like particles (VLPs) of RNA phage Qbeta are stabilized by four disulfide bonds of cysteine residues 74 and 80 within the loop between beta-strands F and G (FG loop) of the monomeric subunits, which determine the five-fold and quasi-six-fold symmetry contacts of the VLPs. In order to reduce the stability of Qbeta VLPs, we mutationally converted the amino acid stretch 76-ANGSCD-81 within the FG loop into the 76-VGGVEL-81 sequence. It led to production in Escherichia coli cells of aberrant rod-like Qbeta VLPs, along with normal icosahedral capsids. The length of the rod-like particles exceeded 4-30 times the diameter of icosahedral Qbeta VLPs.