RESUMO
We have isolated the cDNA for 42Sp48 and EF-1 alpha from mixed stage oocytes and tailbud (stage 22) Xenopus laevis cDNA libraries by use of the cDNA for human elongation factor-1 alpha (EF-1 alpha) as probe. The nucleotide and deduced amino acid sequences of the entire coding region of 42Sp48 and EF-1 alpha cDNA were established. The proposed functional homology of the proteins is reflected in highly conserved amino acid sequences (91% identity), while the large number of silent mutations at the gene level may serve to prevent recombination at their loci. 42Sp48 is apparently encoded by two genes in Xenopus, while no sequences corresponding to 42Sp48 could be found in murine or human genomic DNA. 42Sp48 has been proposed to act as a stage-specific elongation factor in Xenopus. Comparison of the deduced amino acid sequences of 42Sp48 and EF-1 alpha with that of elongation factor Tu from E. coli, for which the three-dimensional structure including that of the GTP binding sites have been determined, supports this hypothesis.
Assuntos
Fatores de Alongamento de Peptídeos/genética , Xenopus laevis/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Southern Blotting , DNA/genética , DNA/isolamento & purificação , Regulação da Expressão Gênica , Genes , Dados de Sequência Molecular , Mutação , Oócitos , Fator 1 de Elongação de Peptídeos , Homologia de Sequência do Ácido Nucleico , Proteínas de XenopusRESUMO
Two-dimensional gel electrophoretic (NEPHGE) analysis of proteins from mouse 3T3B and 3T3B/SV40 cells labelled with [methyl-3H]methionine in the presence of cycloheximide have revealed that the elongation factor 1 alpha (EF-1 alpha) in these cells is methylated and that the extent of methylation is higher in the SV40 transformed cell type. It is suggested that methylation may account for differences in growth properties for the different cell types.
Assuntos
Transformação Celular Viral , Fatores de Alongamento de Peptídeos/metabolismo , Animais , Linhagem Celular , Cicloeximida/farmacologia , Eletroforese em Gel de Poliacrilamida , Fibroblastos/metabolismo , Metilação , Camundongos , Fator 1 de Elongação de Peptídeos , Vírus 40 dos SímiosRESUMO
We have undertaken an immunological and biochemical analysis of the most abundant soluble protein of previtellogenic Xenopus oocytes, 42S p48. We show that this protein shares immunological cross-reactivity with elongation factor 1 alpha (EF-1 alpha). Direct assays of both 42S fractions and purified 42S p48 show that this cross-reactivity is of functional significance since 42S p48, like EF-1 alpha, can transfer charged amino acids to ribosomes. We further demonstrate that 42S p48 is degraded soon after the onset of vitellogenesis, while the EF-1 alpha concentration remains essentially unchanged during this transition. These properties of 42S p48 are discussed with regard to its role in oogenesis.