rack1 was originally isolated and identified as an intracellular protein receptor for protein kinase c, noting the significant homology to the beta subunit of heterotrimeric g proteins. later studies established rack1, and its yeast homolog asc1, as a core ribosomal protein of the eukaryotic small (40s) ribosomal subunit. much of the function of asc1/rack1 appears to result from its position on the 'head' of the 40s ribosomal subunit. asc1/rack1 participates in several aspects of eukaryotic translation and ribosome quality control, including ires-mediated translation, non-stop decay, non-functional 18s ribosomal rna decay, and frameshifting.