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Results for “Peptide Chain Initiation, Translational”

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At least 19 recordsLinked to original sources
PubMed1978

Models for mRNA translation: theory versus experiment.

Three models for mRNA translation are discussed in the light of available experimental data. It is concluded that the elongation rates vary along a messenger, possibly as a result of a coupling between ribosome movement and mRNA secondary structure. Some promising areas of further experimentation are indicated.

Alpha-Globulins↗
PubMed1979

A kinetic model of protein synthesis. Application to hemoglobin synthesis and translational control.

We present a kinetic model of protein synthesis which encompasses initiation, elongation, and termination parameters. We have investigated the dependence of the total rate of protein synthesis and the size of the translating polysomes on each of these parameters and in particular on the level of active 40 S ribosomes and initiation factors. This model qualitatively fits experimental data for the ratio of alpha- to beta-globin synthesis in reticulocytes, both under normal conditions and in the presence of inhibitors of chain initiation. This model has also been used to examine the effect that limiting amounts of certain tRNAs might have on the total rate of protein synthesis. In addition, the role of initiation factor discrimination and mRNA length are examined with respect to the differential translation of mRNAs.

Animals↗
PubMed1979

Acidic ribosomal proteins from eukaryotic cells. Effect on ribosomal functions.

Precipitation of Saccharomyces cerevisiae ribosomes by ethanol under experimental conditions that do not release the ribosomal proteins can affect the activity of the particles. In the presence of 0.4 M NH4Cl and 50% ethanol only the most acidic proteins from yeast and rat liver ribosomes are released. At 1 M NH4Cl two more non-acidic proteins are lost from the ribosomes. The release of the acidic proteins causes a small inactivation of the polymerizing activity of the particles, additional to that caused by the precipitation itself. The elongation-factor-2-dependent GTP hydrolysis of the ribosomes is, however, more affected by the loss of acidic proteins. These proteins can stimulate the GTPase but not the polymerising activity when added back to the treated particles. Eukaryotic proteins cannot be substituted for bacterial acidic proteins L7 and L12. We have not detected immunological cross-reaction between acidic proteins from Escherichia coli and those from yeast, Artemia salina and rat liver or between acidic proteins from these eukaryotic ribosomes among themselves.

GTP Phosphohydrolase-Linked Elongation Factors↗
PubMed1979

Protein synthesis and aging: studies with cell-free mammalian systems.

A cell-free system devoid of polysomes, which translates natural mRNA, has been prepared from rat liver. It contains ribosomal subunits, ribosomes, aminoacyl-tRNA synthetases, tRNAs, and protein factors necessary for translation. Protein synthesis required an energy-generating system, mRNA, and 3 mM Mg2+ concentration, and it was inhibited by 7-methylguanylic acid. The total extent and the rate of protein synthesis were approximately 30% greater when the translating system was prepared from livers of 3-month-old rats, as compared to 30-month-old rats. A ribosome-free fraction containing the protein factors required for translation was also prepared from 3-month-old and 30-month-old rat livers and brains, by extraction with 0.5 M KCl. The high-salt extracts were analyzed for elongation factors EF-1 and EF-2 in a poly(U) translating system. Although the activity of EF-2 was similar in preparations from young and old rats, the EF-1 activity in the 3-month-old rat livers and brains was 30 to 40% greater than in 30-month-old animals. The protein synthesizing activity of high salt-washed ribosomes stripped of endogenous peptidyl-tRNA and mRNA, from livers and brains of young and old animals, was the same.

Aging↗
PubMed1979

Mechanism of interferon action: phosphorylation of protein synthesis initiation factor eIF-2 in interferon-treated human cells by a ribosome-associated kinase processing site specificity similar to hemin-regulated rabbit reticulocyte kinase.

The phosphorylation of purified protein synthesis factors catalyzed by protein kinase preparations isolated from interferon-treated human amnion cells was examined. Ribosomal salt-wash fractions prepared from interferon-treated human cells contained a protein kinase that catalyzed the [gamma-(32)P]ATP-mediated phosphorylation of the 38,000-dalton subunit of eukaryotic initiation factor 2 (eIF-2alpha); this kinase activity was significantly enhanced in interferon-treated as compared to untreated cells. The tryptic [(32)P]phosphopeptide pattern obtained for eIF-2alpha phosphorylated by the interferon-mediated human kinase was indistinguishable from the pattern obtained for eIF-2alpha phosphorylated by the hemin-regulated rabbit reticulocyte kinase when analyzed by thin-layer chromatography with three different solvent systems and by high-voltage electrophoresis. O-[(32)P]Phosphoserine was liberated by partial acid hydrolysis from eIF-2alpha phosphorylated by either the human or the rabbit kinase. In addition to the phosphorylation of eIF-2alpha, interferon treatment of human cells enhanced the phosphorylation of two additional ribosome-associated proteins designated P(1) and P(f). The major phosphoester linkage observed for the human, as well as murine, phosphoprotein P(1) was O-phosphoserine. The interferon-mediated phosphorylation of both eIF-2alpha and protein P(1) was dependent upon the presence of RNA with double-stranded character; P(f) phosphorylation was not affected by double-stranded RNA. These results suggest that the interferon-mediated ribosome-associated human protein kinase catalyzes the phosphorylation of eIF-2alpha in a site-specific manner that is apparently identical with the reaction catalyzed by the hemin-regulated rabbit reticulocyte kinase; hence, the phosphorylation of eIF-2 may play a role in regulating the initiation of translation in interferon-treated cells.

Cells, Cultured↗