Thesaurin a, the major protein of Xenopus laevis previtellogenic oocytes, present in the 42 S particles, is homologous to elongation factor EF‐1α

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Abstract
We have purified in SDS X. laevis thesaurin a (M r 50 000) which is part of the 42 S storage particles. Its N‐terminal amino acid is blocked and several peptides obtained by V8 protease treatment were purified and sequenced. As expected from one of the functional roles of the 42 S particles (tRNA binding, protection against deacylation and exchange with the ribosome), the amino acid sequence of thesaurin a was found to be closely related to that of the elongation factor EF‐1α. We suggest that all three proteins involved in 5 S RNA and tRNA storage in previtellogenic oocytes, TFIIIA, thesaurin a and thesaurin b, have a dual function: storage and a role in transcription or in protein synthesis.