Structure of r-protein L22. (A) Amino acid sequence alignment of r-protein L22 from E. coli (Eco) and Thermus thermophilus (Tth). Amino acids identical in both proteins are indicated by dots in the Tth sequence. (B) Structure of L22 from T. thermophilus L4. The portions of the extended loop removed in the E. coli deletion mutants are indicated on the T. thermophilus structure in red (Δery), green (Δloop1), and blue (removed in Δloop2 together with amino acids indicated in red and green). The wild-type structure (Unge et al. 1998; PDB file 1BXE) and the structure of the L22–Δery mutant (Davydova et al. 2002, PDB file 1I4J) were drawn using RasMol (Bernstein 2000). The actual structures of Δloop1 and Δloop2 are not known; the deleted amino acids were removed from the wild-type L22 model.
