Forms the large subunit's ribosomal stalk, playing a central role in the interaction of the ribosome with elongation 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, although the first site is the most stimulatory. Part of the 50S ribosomal subunit, binds large rRNA. Forms the ribosomal stalk which helps the ribosome interact with GTP-bound translation factors. Forms a heptameric L10(L12)2(L12)2(L12)2 complex, where L10 forms an elongated spine to which the L12 dimers bind in a sequential fashion. Belongs to the universal ribosomal protein uL10 family.