Fig. 1.

Archaeal ribosomal proteins have segments that are similar or identical to NLSs. This figure compares the crystal structures and sequences of homologous ribosomal proteins from Archaea, Bacteria, and Eukarya. NLSs in eukaryotic proteins and corresponding segments in homologous archaeal proteins are highlighted in red. This figure illustrates that NLSs of eukaryotic proteins are absent in homologous bacterial ribosomal proteins, but present in homologous archaeal ribosomal proteins. To compare structural similarity between eukaryotic NLSs and corresponding protein segments in bacterial and archaeal proteins, the RMSD values are shown for superposition of Cα-atoms of NLS segment in eukaryotic protein and a corresponding protein segment in archaeal and bacterial homologs.