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R Amons

Publications and source records attributed to R Amons.

At least 55 records · Page 3Linked to original sources
PubMed1988

Phosphorylation of elongation factor 1 beta by an endogenous kinase affects its catalytic nucleotide exchange activity.

Elongation factor 1 beta (EF-1 beta) from Artemia is phosphorylated to a high percentage at serine 89 by an endogenous kinase present in EF-1 beta gamma. Protein sequencing of EF-1 beta revealed that this serine residue is located N-terminally of an acidic cluster of amino acids, (formula; see text) which is critical for casein kinase II-type substrate recognition. A number of compounds known to influence casein kinases were studied, revealing that the kinase activity as present in EF-1 beta gamma belongs to the class of casein kinase II. The rate of nucleotide exchange on EF-1 alpha as catalyzed by EF-1 beta was found to be affected reversibly by the state of phosphorylation of EF-1 beta. In the presence of dephosphorylated EF-1 beta, the exchange rate is almost twice as large compared to the rate in the presence of phosphorylated EF-1 beta. Rephosphorylation of dephosphorylated EF-1 beta diminishes the activity of the protein again. The role of casein kinase II-type enzymes in modulating the function of proteins involved in polypeptide synthesis is discussed.

Amino Acid Sequence↗
PubMed1987

Primary structure of elongation factor 1 gamma from Artemia.

Complementary DNA corresponding to elongation factor 1 gamma, which forms a complex with EF-1 beta, has been cloned. A lambda gt11 cDNA library has been screened with an antiserum against EF-1 beta gamma. The derived amino acid sequence of EF-1 gamma corresponds to 429 amino acids excluding the initiator methionine, which is absent in the mature protein. About half of the protein was sequenced by direct protein sequence analysis. No clear homology with any other protein was found.

Amino Acid Sequence↗
PubMed1987

Vapor-phase modification of sulfhydryl groups in proteins.

Proteins and peptides are readily and specifically modified at their sulfhydryl groups by the vapors of a mixture of 4-vinylpyridine and tributylphosphine. The phenylthiohydantoin derivative of S-beta-(4-pyridylethyl)cysteine formed during sequence analysis is easily detectable in current identification systems.

Amino Acid Sequence↗
PubMed1987

A conserved amino acid sequence around Arg-68 of Artemia elongation factor 1 alpha is involved in the binding of guanine nucleotides and aminoacyl transfer RNAs.

The rate of trypsin cleavage of elongation factor 1 alpha having bound GDP is low and increases on exchange of GDP for GTP. The cleavage occurs at a unique position of the protein chain, namely at arginine-68 of Artemia EF-1 alpha. This increase in trypsin sensitivity is enhanced further in the presence of charged or uncharged transfer RNA. The local unfolding of EF-alpha at residue 68 is discussed in terms of a model in which GTP hydrolysis controls the positioning of a short 3'-terminal section of transfer RNA near the centre of peptide bond synthesis.

Adenine Nucleotides↗
PubMed1986

Primary structures of mutationally altered ribosomal protein L7/L12 and their effects on cellular growth and translational accuracy.

The amino acid sequences of mutationally altered ribosomal protein L7/L12 from four different rplL mutants of Escherichia coli were determined and correlated with some features of the mutant ribosomes. Two of the rplL mutations are deletions around position 40, which give rise to a shortened hinge region between the two domains of L7/L12. The other two mutants harbor point mutations at position 74 (Gly----Asp) or at position 82 (Glu----Lys), which are in or close to an evolutionarily conserved sequence in the C-terminal domain. The two latter mutations are associated with decreased rates of growth and translational elongation. All four mutants show increased nonsense codon read-through in vivo. Ribosomes from one of the deletion mutants show clearly increased missense error rates in vitro.

Amino Acids↗
PubMed1986

The primary structure of the alpha subunit of human elongation factor 1. Structural aspects of guanine-nucleotide-binding sites.

The primary structure of the alpha subunit of elongation factor 1 (EF-1 alpha) from human MOLT 4 cells was determined by cDNA sequencing. The data show that the conservation of the amino acid sequence is more than 80% when compared with yeast and Artemia EF-1 alpha. An inventory of amino acid sequences around the guanine-nucleotide-binding site in elongation factor Tu from Escherichia coli and homologous amino acid sequences in G proteins, initiation and elongation factors and proteins from the RAS family shows two regions containing conserved sequence elements. Region I has the sequence apolar-Xaa-Xaa-Xaa-Gly-Xaa-Xaa-Yaa-Xaa-Gly-LYs-Thr(Ser)- -Xaa-Xaa-Xaa-Xaa-X-apolar. Except for RAS proteins, Yaa is always an acidic amino acid residue. Region II is characterized by the invariant sequence apolar-apolar-Xaa-Xaa-Asn-Lys-Xaa-Asp. In order to facilitate sequence comparison we have used a graphic display, which is based on the hydrophilicity values of individual amino acids in a sequence.

Amino Acid Sequence↗
PubMed1985

Phosphate-binding sequences in nucleotide-binding proteins.

In the three-dimensional model of adenylate kinase, the phosphate-binding site for AMP and ATP has been identified [Pai, E.F. et al. (1977) J. Mol. Biol. 114, 37--45]. In this region one can distinguish a sequence glycine XXXX glycinelysine. The same sequence is found in many other mononucleotide-binding proteins including elongation factors and oncogenic P21 proteins. Dinucleotide-binding proteins display a pyrophosphate-binding unit with a glycine pattern different from that of mononucleotide-binding proteins. It has been found that P21 ras protein possesses a strand motif typical for (pyro)phosphate binding of a mononucleotide. A single mutation at position 12 can confer oncogenic activity on the protein. Based on the assumption that amino acid residues which are critical for function are preferentially conserved, we predict from the sequence that glycine residue 15 rather than residue 12 is important for (pyro)phosphate binding.

Adenine Nucleotides↗
PubMed1984

The primary structure of elongation factor EF-1 alpha from the brine shrimp Artemia.

cDNA as well as amino acid sequencing has revealed the complete primary structure of elongation factor EF-1 alpha from the brine shrimp Artemia. A comparison with the published sequences of bacterial EF-Tu, mitochondrial EF-Tu and chloroplastic EF-Tu shows that distinct areas of these polypeptide chains are conserved in evolution. The evolutionary distance between prokaryotic and eukaryotic types of EF-Tu is larger than among bacterial and organellar EF- Tus . A number of regions present in both EF-Tu and EF-G from Escherichia coli are also found in EF-1 alpha from Artemia.

Amino Acid Sequence↗
PubMed1983

Sequence homology between EF-1 alpha, the alpha-chain of elongation factor 1 from Artemia salina and elongation factor EF-Tu from Escherichia coli.

In the course of a structural analysis of the alpha-chain of elongation factor 1 from Artemia salina cysts, we present four amino acid sequences comprising together half of the polypeptide chain. A comparison of these sequences with the primary structure of elongation factor EF-Tu from Escherichia coli reveals a clear correspondence between the eukaryotic and prokaryotic protein throughout their polypeptide chains. The results support a basic conservation of the structure of the aminoacyl-tRNA carrying enzyme in evolution. The occurrence, in the eukaryotic factor, of several epsilon-trimethyllysine residues, is remarkable.

Amino Acid Sequence↗
PubMed1982

Ribosomal protein S6 from Xenopus laevis ovaries. Isolation, phosphorylation in vivo and cross-reaction with heterologous anti-S6 antibodies.

Ribosomal protein S6 from Xenopus laevis ovaries was prepared by ion-exchange chromatography on phosphocellulose and gel filtration on Sephadex G-75. The protein was identified as S6 from its position on two-dimensional polyacrylamide gels and from its immunological cross-reaction with monoclonal antibody raised against chicken liver S6, and from the fact that it is the major phosphorylated protein of the small subunit. When oocytes were incubated with [32P]orthophosphate in the presence of progesterone, 32P incorporation of 40-S ribosomal proteins was stimulated about 10-fold over controls without hormone. The bulk of the 32P radioactivity was incorporated into protein S6.

Animals↗
PubMed1978

Isolation and characterization of the acidic phosphoproteins of 60-S ribosomes from Artemia salina and rat liver.

Eucaryotic L7/L12-type proteins are present in ethanol/salt extracts (P1 protein) of ribosomes from Artemia salina and rat liver. These proteins are partially phosphorylated and occur in two forms of closely related structure: a major form eL12 having methionine at the N-terminal position and a minor form of eL12 (eL12') which seems slightly elongated and contains a blocked N terminus. Purification of the four different forms of this protein, eL12, eL12-P, eL12' and eL12'-P, was performed by ion-exchange chromatography on carboxymethyl-cellulose and DEAE-cellulose. Using a radioimmuno assay, 1.8 copies of eL12 and 0.9 of eL12' were found on the 80-S A. salina ribosome. In ribosomes of both rat liver and A. salina, eL12 is present in a larger quantity than eL12'. 40-S and 60-S ribosomal subunits extracted with ethanol/salt were essentially free of eL12 proteins. A large pool of eL12 was found in the cytosol after removal of the ribosomes by centrifugation or molecular sieving. The proteins of rat liver and A. salina are similar with regard to their isoelectric points and molecular weights. Sedimentation equilibrium studies indicated that the isolated protein eL12 occurs as a dimer.

Amino Acids↗
PubMed1975

Isolation and characterization of two acidic proteins of 60s ribosomes from Artemia salina cysts.

60S ribosomes from encysted gastrulae of the brine shrimp Artemia salina contain two acidic proteins, which are homologous to the Escherichia coli proteins L7 and L12. The proteins were purified and characterized with respect to molecular weight, amino-acid composition, peptide maps, and their functional requirement in the elongation factor dependent binding of aminoacyl transfer RNA to the ribosome.

Amino Acids↗