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-protei n, 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. cerev isiae has been identified as a primary rRNA-binding protein that directly b inds to a specific site on yeast 26S rRNA. It is translocated to the nucleo lus where it binds to 26S rRNA during early large ribosome subunit assembly ; this binding is thought to play an important role in ribosome assembly. T he S. cerevisiae mutant strain YCR61 expresses L25 when grown on galactose, but not glucose, medium. Transformation of YCR61 with a shuttle vector con taining the AtRPL23A-1 cDNA allowed transformed colonies to grow in and on glucose selection medium. R-protein AtRPL23A-1 can complement the L25 mutat ion, demonstrating the functional equivalence of the two r-proteins and int roducing AtRPL23A-1 as the first plant member of the L23/L25 r-protein fami ly.