THE LEUCINE-ZIPPER IN ELONGATION-FACTOR EF-1-DELTA, A GUANINE-NUCLEOTIDE EXCHANGE PROTEIN, IS CONSERVED IN ARTEMIA AND XENOPUS

Elongation factor 1, a complex involved in protein biosynthesis, conta ins two guanine-nucleotide-exchange proteins EF-1 delta and EF-1 delta . The sequence of EF-1 delta of Artemia was determined with the purifi ed protein. When compared to EF-1 delta from Xenopus, a high degree of identity (80%) was found in the C-terminal domains of the proteins, w hich contain the guanine-nucleotide-exchange activity. The N-terminal domains share only 23% of the amino acids at identical positions, and therefore they were further analysed for less obvious types of homolog y. To this end, a published approach for sequence analysis, which can detect peculiar amino acid patterns in proteins was applied. In this w ay, a weak albeit unmistakable similarity between the two EF-1 delta p roteins was demonstrated in the region of the leucine-zippers, apart f rom the leucine repeat itself. Apparently, they display a common struc tural pattern in their N-terminal domains, which so far has been obser ved mainly in transcription factors.