42Sp48 in previtellogenic Xenopus oocytes is structurally homologous to EF-1 alpha and may be a stage-specific elongation factor.

Abstract

Abstract. We have isolated the cDNA for 42Sp48 and EF-la from mixed stage oocytes and tailbud (stage 22) Xenopus laevis cDNA libraries by use of the cDNA for human elongation factor-ltx (EF-lo0 as probe. The nucleotide and deduced amino acid sequences of the entire coding region of 42Sp48 and EF-hx 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-lo~ with that of elongation factor Tu from E. coli, for which the three-dimensional structure including that of the GTP binding site have been determined, supports this hypothesis.OGENESIS in amphibians can be divided into two distinctive stages; previteLlogenesis, in which the cytoplasm of the cell is devoid of yolk and is transparent, and viteUogenesis, in which yolk, lipids, glycogen, and ribosomes rapidly accumulate. An oocyte of the African clawed toad, Xenopus laevis, contains extremely large amounts of RNA, 95 % of which is ribosomal in origin and 2 % of which is tRNA, while the remainder is thought to be mRNA (Brown and Littna, 1964). The oocyte transcribes 5S rRNA and tRNA genes constantly during all stages of growth and during previtellogenesis, in which the amplified 28S and 18S rRNA genes are not transcribed, 80% of the total RNA content comprises 5S and tRNA species (Ford, 1971). These components are stored in two cytoplasmic ribonucleoprotein particles, the 7S and 42S ribonucleoprotein particles (Denis

The Role of Xenopus Membrane Progesterone Receptor β in Mediating the Effect of Progesterone on Oocyte Maturation

“…The images were captured with a Fluorchem 8900 analyzer (Alpha Innotech, San Leandro, CA). PCR products were sequenced and were found to be 99% identical to reported sequences of XmPR␤ and 100% identical to reported Ef1a (52).…”

Contribution of Individual Amino Acids to the 5S RNA Binding Activity of the Xenopus Zinc Finger Protein p43

“…In comparison, the 42S RNP is a tetrameric complex of 15S subunits consisting of p48 protein, a p43 protein, tRNA and 5S RNA in the molar ratio of 2:1:3:1 ,, . The p48 protein is an EF-1α-type protein that interacts with a variety of aminoacyl-tRNAs in the 42S RNP – while the p43 protein binds to the 5S RNA. Sequence analysis of the cDNAs of TFIIIA and p43 has shown that each contains 9 tandem zinc fingers – .…”

A mitochondrial elongation factor‐like protein is over‐expressed in tumours and differentially expressed in normal tissues

“…Although this protein might simply be a tissue specific protein which cross-reacts with the antibody it warrants further investigation as it might be a related protein with a different function or a modified form of P43 found only in the lung. In this respect it is interesting to note that eukaryotic protein elongation factors are increasingly being shown to be involved in functions other than protein synthesis, such as organisation of the mitotic apparatus [20], developmental regulation [21,22], aging [23], signal transduction [24] and transformation [25]. The increased expression of the human cytoplasmic elongation factor EF-la in adenocarcinomas has also been recently reported [26].…”