Structural and functional properties of thesaurin a (42Sp50), the major protein of the 42 S particles present in Xenopus laevis previtellogenic oocytes.
Thesaurin a is one of two protein components of a 42 S ribonucleoprotein particle that is very abundant in previtellogenic oocytes of Xenopus laevis. The primary function of the 42 S particle is the long-term storage of 5 S RNA and aminoacyl-tRNA. Thesaurin a is homologous to eukaryotic elongation factor 1 alpha (EF-1 alpha) and to prokaryotic elongation factor Tu (EF-Tu). Sequence comparison with EF-1 alpha and EF-Tu of different species indicates that thesaurin a is rather distantly related to all eukaryotic elongation factors. In spite of this, the secondary structure of thesaurin a, deduced from hydrophobic cluster analysis, is remarkably similar to that of EF-1 alpha and EF-Tu. The binding and catalytic properties of thesaurin a are also similar but not identical to those of EF-1 alpha. Like EF-1 alpha, purified thesaurin a binds tRNA, GDP, and GTP. Unlike EF-1 alpha, thesaurin a binds discharged tRNA more tightly than charged tRNA, and GTP more tightly than GDP. Thesaurin a also hydrolyzes GTP and catalyzes the mRNA-dependent binding of aminoacyl-tRNA to 80 S ribosomes. The functional properties of the 42 S particle are in general agreement with those of purified thesaurin a. In particular, the 42 S particle contains GTP and efficiently transfers aminoacyl-tRNA to 80 S ribosomes without addition of exogenous elongation factor.
Viel
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Centre de Génétique Moléculaire, Laboratoire propre du Centre National de la Recherche Scientifique (CNRS) associé à l'Université P. et M. Curie, Gif-sur-Yvette, France.
le Maire
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Philippe
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Morales
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J
Mazabraud
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Denis
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H
D000595:Amino Acid Sequence; D000818:Animals; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D008969:Molecular Sequence Data; D015689:Oncogene Protein p21(ras) / Q000235:genetics; D009865:Oocytes / Q000378:metabolism*; D020648:Peptide Elongation Factor 1; D010444:Peptide Elongation Factor Tu / Q000235:genetics; D010445:Peptide Elongation Factors / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D011487:Protein Conformation; D012343:RNA, Transfer / Q000378:metabolism; D014818:Vitellogenesis; D029867:Xenopus Proteins; D014982:Xenopus laevis
D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors; D029867:Xenopus Proteins; C066976:thesaurin A; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D012343:RNA, Transfer; D010444:Peptide Elongation Factor Tu; D015689:Oncogene Protein p21(ras)