CHARACTERIZATION OF YEAST EF-1-ALPHA - NONCONSERVATION OF POSTTRANSLATIONAL MODIFICATIONS

Elongation factor 1alpha (EF-1alpha) is an abundant cellular protein and its amino-acid sequence has been inferred from numerous organisms, including bacteria, archaebacteria, plants and animals. In large measure, it would appear that the overall structure has probably been maintained given the 33% identity and 56% similarity of Escherichia coli EF-Tu with human EF-1alpha. Chemical sequencing of EF-Tu and EF-1alpha has revealed that these proteins are post-translationally modified. In order to assess the possible function of these modifications, we have chemically sequenced the EF-1alpha from the lower eukaryote Saccharomyces cerevisiae (yeast). To our surprise, the methylation pattern of yeast EF-1alpha was quite different from either rabbit or brine shrimp EF-1alpha with only the trimethyllysine at position 79 conserved although the yeast protein is 81% identical to rabbit EF-1alpha. A dimethyllysine was observed at position 316 which corresponds to a trimethyllysine in brine shrimp and rabbit EF-1alpha. The other positions in yeast EF-1alpha which were methylated were unrelated to the other six possible positions for modification observed in brine shrimp or rabbit EF-1alpha. In addition, the unique glycerylphosphorylethanolamine observed in mammalian EF-1alpha and suspected in brine shrimp EF-la was not found in yeast EF-1alpha.