The "40S" and "60S" names originate from the convention that ribosomal particles are denoted according to their sedimentation coefficients in Svedberg units.
The 40S subunit contains the decoding center which monitors the complementarity of tRNA and mRNA in protein translation.
[6] The 40S ribosomal subunit is also tightly bound by the HCV IRES to form a binary complex mediate by protein-mRNA and rRNA-mRNA interactions.
Proteins which have homologs in eukaryotes, archaea and bacteria (EAB) are shown as blue ribbons.
Eukaryote-specific extensions of conserved proteins, ranging from a few residues or loops to very long alpha helices and additional domains, are highlighted in red.