[Phosphoprotein phosphatases].
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Animals↗
Biomedical subjects
E Paleń
Publications and source records attributed to E Paleń.
Phosphoprotein phosphatase from yeast and its ribosomal substrate.
Phosphoprotein phosphatase was isolated from yeast postribosomal supernatant and partly characterized. The enzyme preferentially dephosphorylated phospho-casein and acidic ribosomal proteins L44 and L45, the eukaryotic analogues of bacterial proteins L7 and L12. The evidence suggests that this enzyme is not a catalytic subunit of the multifunctional phosphoprotein phosphatase present in most eukaryotic organisms.
Fungal Proteins↗
Yeast ribosome core particles deficient in acidic proteins L44 and L45 and their activity in reconstitution experiments.
The yeast ribosome core particles partly depleted of acidic proteins, L44 and L45, were isolated and their activity was examined using a highly purified protein synthesizing system. It was shown that both the phenylalanine polymerization reaction and the elongation factor 2-dependent GTP hydrolysis were stimulated by the addition of the extracted acidic protein fraction. The results obtained clearly indicate a functional role of these proteins in the elongation step of eukaryotic protein synthesis. The essential parameters of ribosome reconstitution experiments are discussed.
Fungal Proteins↗
An inhibitory effect of cyclic nucleotide-independent protein kinases on protein synthesis in vitro.
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Cell-Free System↗
Isolation and properties of elongation factor 1 from Saccharomyces cerevisiae.
Polypeptide elongation factor 1 was isolated from yeast postribosomal supernatant. The highly purified factor was resolved on Ultrogel AcA-44 into two complementary fractions. One of these fractions contained two different polypeptide chains corresponding to a Ts-like elongation factor EF-1 beta gamma. The other fraction represented the light form of the factor, designated EF-1 alpha, with a molecular weight of approximately 50,000. The obtained results indicate that EF-1 from lower eukaryotes is also composed of three distinct polypeptides.
Fungal Proteins↗
Evidence for a highly specific protein kinase phosphorylating two strongly acidic proteins of yeast 60 S ribosomal subunit.
Two distinct, cyclic AMP-independent protein kinase (ATP : protein photransferase, EC 2.7.1.37) from yeast have been isolated and highly purified. The first of the enzymes, protein kinase 1 A, phosphorylates casein and phosvitin, and its cellular protein substrate is unknown. The second enzyme, protein kinase 1 B, phosphorylates two strongly acidic proteins, L44 and L45, of the 60 S ribosomal subunit.
Adenosine Triphosphate↗
The effect of sulfhydryl reagents on the activity and stability of yeast ribosomes.
By titration with N-ethylmaleimide (MalNet) and p-chloromercuribenzoate (pCMB) of native yeast ribosomes, 40-43 SH groups were found, which represent about one third of the total SH groups present in these ribosomes. The reaction with pCMB proceeded fast, and that with MalNet was slow. The SH-blocking reaction led to inhibition of the ribosome activity. The activity of the MalNet-treated ribosomes in the polymerization reaction decreased concomitantly with the decrease of their activity in the enzymic and non-enzymic binding of phenylalanyl-tRNA and N-acetylphenylalanyl-tRNA. pCMB completely inactivated the ribosomes which seems to indicate that this reagent modified some SH groups which were not accessible to MalNet. The ribosome stability was affected by the blocking of the SH groups; in the buffered 0.5 M-KCl solution a significant portion of protein was detached from the modified ribosomes. Thus it appears that the SH groups of ribosomal proteins play some role in maintaining the ribosome structure.
Chloromercuribenzoates↗
Proteins of yeast ribosomal subunits: number and general properties.
1. Saccharomyces cerevisiae at the early stationary phase of growth accumulate 80 S ribosomes, easily dissociating into subunits, which retain full activity in phenylalanine polymerization in vitro. A simplified and efficient technique for large-scale preparation of yeast ribosomal subunits is proposed. 2. Presence of 34 proteins in 40 S subunit and 42 proteins in 60 S subunit was demonstrated by two-dimensional acrylamide-gel electrophoresis. Both ribosomal subunits contain acidic proteins: three in 60 S and six or seven in 40 S subunit. It seems that two of them correspond to prokaryotic proteins, L7 and L12. The total number of yeast ribosomal proteins is similar to those obtained for other Eukaryota.
Centrifugation, Zonal↗