Acidic Phosphoproteins P1 Research Articles

The N‐terminal regions of eukaryotic acidic phosphoproteins P1 and P2 are crucial for heterodimerization and assembly into the ribosomal GTPase‐associated center

Acidic phosphoproteins P1 and P2 form a heterodimer and play a crucial role in assembly of the GTPase-associated center in eukaryotic ribosomes and in ribosomal interaction with translation factors. We investigated the structural elements within P1 and P2 essential for their dimerization and for ribosomal function. Truncation of the N-terminal 10 amino acids in either P1 or P2 and swapping of the N-terminal 10 amino acid sequences between these two proteins disrupted their dimerization, binding to P0 and P0 binding to rRNA. In contrast, truncation of the C-terminal halves of P1 and P2 as well as swapping of these parts between them gave no significant effects. The protein dimers containing the C-terminal truncation mutants or swapped variants were assembled with P0 onto Escherichia coli 50 S subunits deficient in the homologous protein L10 and L7/L12 and gave reduced ribosomal activity in terms of eukaryotic elongation factor dependent GTPase activity and polyphenylalanine synthesis. The results indicate that the N-terminal 10 amino acid sequences of both P1 and P2 are crucial for P1-P2 heterodimerization and for their functional assembly with P0 into the GTPase-associated center, whereas the C-terminal halves of P1 and P2 are not essential for the assembly.

Ribosomal acidic phosphoproteins P1 and P2 are not required for cell viability but regulate the pattern of protein expression in Saccharomyces cerevisiae.

Saccharomyces cerevisiae strains with either three inactivated genes (triple disruptants) or four inactivated genes (quadruple disruptants) encoding the four acidic ribosomal phosphoproteins, YP1 alpha, YP1 beta, YP2 alpha, and YP2 beta, present in this species have been obtained. Ribosomes from the triple disruptants and, obviously, those from the quadruple strain do not have bound P proteins. All disrupted strains are viable; however, they show a cold-sensitive phenotype, growing very poorly at 23 degrees C. Cell extracts from the quadruple-disruptant strain are about 30% as active as the control in protein synthesis assays and are stimulated by the addition of free acidic P proteins. Strains lacking acidic proteins do not have a higher suppressor activity than the parental strains, and cell extracts derived from the quadruple disruptant do not show a higher degree of misreading, indicating that the absence of acidic proteins does not affect the accuracy of the ribosomes. However, the patterns of protein expressed in the cells as well as in the cell-free protein system are affected by the absence of P proteins from the particles; a wild-type pattern is restored upon addition of exogenous P proteins to the cell extract. In addition, strains carrying P-protein-deficient ribosomes are unable to sporulate but recover this capacity upon transformation with one of the missing genes. These results indicate that acidic proteins are not an absolute requirement for protein synthesis but regulate the activity of the 60S subunit, affecting the translation of certain mRNAs differently.

Nucleotide sequence of a cDNA encoding ribosomal acidic phosphoprotein P1 fromDictyostelium discoideum: identification of a novel carboxy-terminal sequence in ‘A’ proteins

Journal Article Nucleotide sequence of a cDNA encoding ribosomal acidic phosphoprotein P1 from Dictyostelium discoideum: identification of a novel carboxy-terminal sequence in ‘A’ proteins Get access Jesús Prieto, Jesús Prieto Departamento de Bioquímica, Facultad de Medicina de la Universidad Autónoma de Madrid and Instituto de Investigaciones Biomédicas del CSICArzobispo Morcillo, 4. 28029 Madrid, Spain Search for other works by this author on: Oxford Academic PubMed Google Scholar Elena Candel, Elena Candel Departamento de Bioquímica, Facultad de Medicina de la Universidad Autónoma de Madrid and Instituto de Investigaciones Biomédicas del CSICArzobispo Morcillo, 4. 28029 Madrid, Spain Search for other works by this author on: Oxford Academic PubMed Google Scholar Antonio Coloma Antonio Coloma Departamento de Bioquímica, Facultad de Medicina de la Universidad Autónoma de Madrid and Instituto de Investigaciones Biomédicas del CSICArzobispo Morcillo, 4. 28029 Madrid, Spain Search for other works by this author on: Oxford Academic PubMed Google Scholar Nucleic Acids Research, Volume 19, Issue 6, 25 March 1991, Page 1340, https://doi.org/10.1093/nar/19.6.1340 Published: 25 March 1991 Article history Received: 02 January 1991 Published: 25 March 1991

Role of acidic phosphoproteins in the partial reconstitution of the active 60 S ribosomal subunit

We have recently shown that rat liver 60 S ribosomal subunits active in protein synthesis can be reconstituted from inactive core particles lacking 30% of the total proteins, mainly L10a, L12, L22, L24, A33 and the acidic phosphoproteins P1–P2, obtained by treatment of 60 S subunits with dimethylmaleic anhydride [(1987) Eur. J. Biochem. 163, 15–20]. In this study, an ethanol extract of the 60 S subunit which contains only P1–P2 was also shown to be effective in reconstitution with the DMMA-core-particies: it strongly stimulated the EF-2-dependent GTP hydrolysis and, to a lesser extent, polyphenylalanine synthesis; like the DMMA wash it shifted the thermal denaturation curve of the DMMA-core particles towards that of control subunits. Prior dephosphorylation of the ethanol extract by alkaline phosphatase inhibited the reconstruction process.