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, contains two guanine-nucleotide-exchange proteins EF-1 beta and EF-1 delta. The sequence of EF-1 delta of Artemia was determined with the purified protein. When compared to EF-1 delta from Xenopus, a high degree of identify (80%) was found in the C-terminal domains of the proteins, which 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 homology. To this end, a published approach for sequence analysis, which can detect peculiar amino acid patterns in proteins was applied. In this way, a weak albeit unmistakable similarity between the two EF-1 delta proteins was demonstrated in the region of the leucine-zippers, apart from the leucine repeat itself. Apparently, they display a common structural pattern in their N-terminal domains, which so far has been observed mainly in transcription factors.

Identification of the maltose transport protein of Saccharomyces cerevisiae.

Identification of the maltose transport protein of Saccharomyces cerevisiae was attempted by searching for maltose-inducible proteins in isolated plasma membranes. Membranes from maltose-grown cells contained two proteins that were absent in glucose-grown cells. The proteins differed in size, but peptide sequence analysis indicated a high degree of homology. The amino-terminal and internal sequences of the largest protein, with an apparent molecular mass of 64 kDa, were determined. These sequences were identical to predicted amino acid sequences in the MAL61 gene product. It is concluded that this protein is the inducible maltose permease of Saccharomyces cerevisiae.