Forms part of the ribosomal stalk, playing a central role in the interaction of the ribosome with GTP-bound translation factors. The stalk complex of P.horikoshii binds to E.coli large subunits and confers on them the ability to interact with eukaryotic elongation factors. Each succesive L12 dimer bound along the P0 spine increases the GTPase activity of elongation factors and increases translation by reconsituted ribosomes. Part of the 50S ribosomal subunit. Homodimer, it forms part of the ribosomal stalk which helps the ribosome interact with GTP-bound translation factors. Forms a heptameric P0(L12)2(L12)2(L12)2 complex, where P0 forms an elongated spine to which the L12 dimers bind in a sequential fashion. Belongs to the eukaryotic ribosomal protein P1/P2 family. Extended N-terminus.