Structural comparison of the prokaryotic ribosomal proteins L7/L12 and L30

The structure of two prokaryotic ribosomal proteins, the carboxyterminal half of L7/L12 from Escherichia coli (L12CTF) and 1.30 from Bacilus Stearothermophilus display a remarkably similar fold in which alpaha‐helices pack onto one side of an antiparallel, three‐stranded, beta‐pleated sheet. A detailed comparison of the structures by least‐squares methods reveals that more than two‐thirds of the alpha carbons can be superimposed with a root mean square distance of 2.33 Å. The principal difference is an extra alpha‐helix in L12 CTF. The sequences of the proteins display a distinct conservation in regions which are crucial to the common fold, in particular the hydrophobic core. It is proposed that the similarity is a result of divergent evolution.