Further observations on the polynucleotide-induced stimulation of protein synthesis by cell-free preparations from rabbit reticulocytes.
Ontology highlight
ABSTRACT:
SUBMITTER: Nair KG
PROVIDER: S-EPMC1264681 | biostudies-other | 1965 Nov
REPOSITORIES: biostudies-other
Similar Datasets
Project description:An extract was prepared from rabbit reticulocyte ribosomes after treatment with potassium chloride as described by Miller, Hamada, Yang, Cohen & Schweet (1967). This extract has been shown to convert monoribosomes into polyribosomes during protein synthesis in vitro (Cohen, 1968). The nature of this extract was studied in greater detail. Centrifugation of the extract through a sucrose density gradient separated the activity into a fast-sedimenting fraction. The two fractions were shown to have different functions in stimulating cell-free protein synthesis and their active components were shown to be protein or partly protein in nature. Each fraction was analysed by electrophoresis and in the analytical ultracentrifuge. It was concluded that the active component in the fast-sedimenting fraction had a sedimentation coefficient of 15.5s and that of the slow-sedimenting fraction 10.5s.
| S-EPMC1185133 | biostudies-other
Project description:1. The incorporation of labelled valine by rabbit reticulocytes into the N-terminal position of nascent haemoglobin was investigated by deaminating the nascent peptides with nitrous acid and isolating labelled alpha-hydroxyisovaleric acid and valine after acid hydrolysis. 2. The amount of radioactivity in alpha-hydroxyisovaleric acid relative to that in valine indicated the presence of 12.3% N-terminal valine having a free amino group. This high value suggests that most if not all nascent peptides contain valine in the N-terminal position. 3. Cell-free preparations containing reticulocyte ribosomes and pH5 enzymes incorporated alpha-hydroxy-[(14)C]isovaleryl-tRNA (where tRNA refers to transfer RNA), which was obtained by deamination of [(14)C]valyl-tRNA from yeast or liver with nitrous acid, into both soluble and nascent protein. 4. When the soluble protein was chromatographed on CM-cellulose, radioactivity was found to be associated with both the alpha-and beta-globin chains. 5. The kinetics of hydrolysis of [(14)C]valine, was also investigated. Most of the material was hydrolysed rapidly at pH10, but a minor component that was relatively stable appeared to be present to the extent of about 10% of the total valyl-tRNA. Valine was, however, the only hydrolysis product detected by paper chromatography. 6. It is concluded that chain initiation in haemoglobin synthesis involves valine as the N-terminal amino acid and that the amino group of nascent protein is probably not substituted.
| S-EPMC1185076 | biostudies-other
Project description:Turnover of mRNA is a critical step that allows cells to control gene expression. Endoribonucleases, enzymes cleaving RNA molecules internally, are some of the key components of the degradation process. Here we provide a detailed characterization of novel endoribonuclease SLFN14 purified from rabbit reticulocyte lysate. Schlafen genes encode a family of proteins limited to mammals. Their cellular function is unknown or incompletely understood. In reticulocytes, SLFN14 is strongly overexpressed, represented exclusively by the short form, all tethered to ribosomes, and appears to be one of the major ribosome-associated proteins. SLFN14 binds to ribosomes and ribosomal subunits in the low part of the body and cleaves RNA but preferentially rRNA and ribosome-associated mRNA. This results in the degradation of ribosomal subunits. This process is strictly Mg(2+)- and Mn(2+)-dependent, NTP-independent, and sequence nonspecific. However, in other cell types, SLFN14 is a full-length solely nuclear protein, which lacks ribosomal binding and nuclease activities. Mutational analysis revealed the ribosomal binding site and the aspartate essential for the endonucleolytic activity of protein. Only few endoribonucleases participating in ribosome-mediated processes have been characterized to date. Moreover, none of them are shown to be directly associated with the ribosome. Therefore, our findings expand the general knowledge of endoribonucleases involved in mammalian translation control.
| S-EPMC4461289 | biostudies-literature
Project description:During the past five years many patients suffering from congenital myasthenic syndromes (CMS) have been identified worldwide and novel causative genes and mutations have been discovered. The disease genes now include those encoding each subunit of the acetylcholine receptor (AChR), the ColQ part of acetylcholinesterase (AChE), choline acetyltransferase, Na(v)1.4, MuSK, and Dok-7. Moreover, emerging genotype-phenotype correlations are providing clues for targeted mutation analysis. This review focuses on the recent observations in selected CMS.
| S-EPMC3478107 | biostudies-literature
Project description:1. Cell-free solutions prepared from rabbit reticulocytes were not able to release iron from rabbit transferrin. 2. The results, which differ from those obtained with Rana catesbeiana immature erythrocytes, indicate that cellular integrity is a requirement for this process in the rabbit reticulocyte system.
| S-EPMC1163994 | biostudies-other
Project description:When radioiron-labelled transferrin with 55Fe located predominantly in the N-terminal iron-binding site and 59Fe predominantly in the C-terminal iron-binding site was incubated with rabbit reticulocytes, both radioisotopes of iron were removed at similar rates. Electrophoresis of transferrin samples taken during the course of an incubation, in polyacrylamide gels containing 6 M-urea, showed that iron was removed in a pairwise fashion, giving rise to iron-free transferrin.
| S-EPMC1158529 | biostudies-other
Project description:KCl cotransport (KCC) activity contributes to pathologic dehydration in sickle (SS) red blood cells (RBCs). KCC activation by urea was measured in SS and normal (AA) RBCs as Cl-dependent Rb influx. KCC-mediated volume reduction was assessed by measuring reticulocyte cellular hemoglobin concentration (CHC) cytometrically. Urea activated KCC fluxes in fresh RBCs to levels seen in swollen cells, although SS RBCs required lower urea concentrations than did normal (AA) RBCs. Little additional KCC stimulation by urea occurred in swollen AA or SS RBCs. The pH dependence of KCC in "euvolemic" SS RBCs treated with urea was similar to that in swollen cells. Urea triggered volume reduction in SS and AA reticulocytes, establishing a higher CHC. Volume reduction was Cl dependent and was limited by the KCC inhibitor, dihydro-indenyl-oxyalkanoic acid. Final CHC depended on urea concentration, but not on initial CHC. Under all activation conditions, volume reduction was exaggerated in SS reticulocytes and produced higher CHCs than in AA reticulocytes. The sulfhydryl-reducing agent, dithiothreitol, normalized the sensitivity of KCC activation to urea in SS RBCs and mitigated the urea-stimulated volume decrease in SS reticulocytes, suggesting that the dysfunctional activity of KCC in SS RBCs was due in part to reversible sulfhydryl oxidation.
| S-EPMC1794068 | biostudies-literature
Project description:We aim to study the rotating and expanding gas in the Red Rectangle, which is a well known object that recently left the asymptotic giant branch (AGB) phase. We analyze the properties of both components and the relation between them. Rotating disks have been very elusive in post-AGB nebulae, in which gas is almost always found to be in expansion.We present new high-quality ALMA observations of C17O J=6-5 and H13CN J=4-3 line emission and results from a new reduction of already published 13CO J=3-2 data. A detailed model fitting of all the molecular line data, including previous maps and single-dish observations of lines of CO, CII, and CI, was performed using a sophisticated code that includes an accurate nonlocal treatment of radiative transfer in 2D. These observations (of low- and high-opacity lines requiring various degrees of excitation) and the corresponding modeling allowed us to deepen the analysis of the nebular properties. We also stress the uncertainties, particularly in the determination of the boundaries of the CO-rich gas and some properties of the outflow.We confirm the presence of a rotating equatorial disk and an outflow, which is mainly formed of gas leaving the disk. The mass of the disk is ~ 0.01 M?, and that of the CO-rich outflow is around ten times smaller. High temperatures of ? 100 K are derived for most components. From comparison of the mass values, we roughly estimate the lifetime of the rotating disk, which is found to be of about 10000 yr. Taking data of a few other post-AGB composite nebulae into account, we find that the lifetimes of disks around post-AGB stars typically range between 5000 and more than 20000 yr. The angular momentum of the disk is found to be high, ~ 9 M? AU km s-1, which is comparable to that of the stellar system at present. Our observations of H13CN show a particularly wide velocity dispersion and indicate that this molecule is only abundant in the inner Keplerian disk, at ? 60 AU from the stellar system. We suggest that HCN is formed in a dense photodissociation region (PDR) due to the UV excess known to be produced by the stellar system, following chemical mechanisms that are well established for interstellar medium PDRs and disks orbiting young stars. We further suggest that this UV excess could lead to an efficient formation and excitation of PAHs and other C-bearing macromolecules, whose emission is very intense in the optical counterpart.
| S-EPMC5166967 | biostudies-literature
Project description:HLA class I alleles constitute established risk factors for non-infectious uveitis and preemptive genotyping of HLA class I alleles is standard practice in the diagnostic work-up. The HLA-A29 serotype is indispensable to Birdshot Uveitis (BU) and renders this enigmatic eye condition a unique model to better understand how the antigen processing and presentation machinery contributes to non-infectious uveitis or chronic inflammatory conditions in general. This review will discuss salient points regarding the protein structure of HLA-A29 and how key amino acid positions impact the peptide binding preference and interaction with T cells. We discuss to what extent the risk genes ERAP1 and ERAP2 uniquely affect HLA-A29 and how the discovery of a HLA-A29-specific submotif may impact autoantigen discovery. We further provide a compelling argument to solve the long-standing question why BU only affects HLA-A29-positive individuals from Western-European ancestry by exploiting data from the 1000 Genomes Project. We combine novel insights from structural and immunopeptidomic studies and discuss the functional implications of genetic associations across the HLA class I antigen presentation pathway to refine the etiological basis of Birdshot Uveitis.
| S-EPMC7687429 | biostudies-literature
Project description:1. A lactating rabbit mammary-gland microsomal system catalysed the incorporation of mannose from GDP-[U-14C]mannose into three endogenous acceptors, (i) polyprenyl phosphate mannose, (ii) lipid-linked oligosaccharide and (iii) protein. 2. Synthesis of polyprenyl phosphate mannose was stimulated by addition of dolichol phosphate to the incubation medium and was reversed by addition of GDP. The product had properties identical with those of authentic dolichol phosphate mannose. 3. The oligosaccharides derived from acid hydrolysis of the lipid-linked oligosaccharide fraction were of six, eight and nine to ten monosaccharide units, the octasaccharide being the major species formed. The oligosaccharide appeared to be attached to the lipid via a pyrophosphate bridge, since strong alkaline hydrolysis liberated an oligosaccharide phosphate. 4. Polyprenyl phosphate mannose served as a mannose donor to lipid-linked oligosaccharides and protein. When added as exogenous substrate it gave rise to a lipid-linked oligosaccharide of about six units. 5. Incorporation of radioactivity in protein was low, but polyacrylamide-gel electrophoresis of the protein fractions indicated that polypeptides of mol.wts. 115000, 75000 and 33000 were labelled.
| S-EPMC1183922 | biostudies-other