Abstract
Antibodies were raised against eukaryotic (rat liver) and prokaryotic (E. coli) ribosomal particles and ribosomal proteins. The antisera were characterized and used to determine the identity of the eukaryotic proteins homologous to E. coli L7 and L12. The large subunit of rat liver ribosomes contains two acidic proteins, L40 and L41; they migrate during two-dimensional polyacrylamide gel electrophoresis in a way that mimics the behavior of L7 and L12. Rat liver L40 and L41 were found to be immunologically related to E. coli L7/L12, hence the proteins are likely to share some structural homology.