Establishment of Arabidopsis thaliana ribosomal protein RPL23A-1 as a functional homologue of Saccharomyces cerevisiae ribosomal protein L25.

Arabidopsis thaliana ribosomal protein (r-protein) RPL23A-1 shows 54% amino acid sequence identity to the Saccharomyces cerevisiae equivalent r-protein, L25. AtRPL23A-1 also shows high amino acid sequence identity to members of the L23/L25 r-protein family in other species. R-protein L25 in S. cerevisiae has been identified as a primary rRNA-binding protein that directly binds to a specific site on yeast 26S rRNA. It is translocated to the nucleolus where it binds to 26S rRNA during early large ribosome subunit assembly; this binding is thought to play an important role in ribosome assembly. The S. cerevisiae mutant strain YCR61 expresses L25 when grown on galactose, but not glucose, medium. Transformation of YCR61 with a shuttle vector containing the AtRPL23A-1 cDNA allowed transformed colonies to grow in and on glucose selection medium. R-protein AtRPL23A-1 can complement the L25 mutation, demonstrating the functional equivalence of the two r-proteins and introducing AtRPL23A-1 as the first plant member of the L23/L25 r-protein family.