1.   c.52.1        Restriction endonuclease-like    
                   Restriction endonuclease-like core: 3 layers, a/b/a; mixed beta-sheet of 5 strands, order 12345; strands 2 &, in some families, 5 are antiparallel to the rest
                   2ot9  d2ot9a1  A:4-18,19-33,36-51,54-58,146-156
                   2g3w  d2g3wa1  A:4-18,23-33,36-51,55-60,148-158

2.   b.168.1       HisI-like    
                   HisI-like pseudo barrel, capped by an alpha-helix; contains a beta-triangle structure on one side; some topological similarity to the Ribosomal protein L25-like fold (scop_cf 50714) and the N-terminal domain of Glutamine synthetase (scop_sf 54368)
                   1zps  d1zpsb1  B:23-32,33-43,43-54,56-62,89-99
                   1zps  d1zpsa1  A:23-32,33-43,43-54,56-62,89-99

3.   b.53.1        Ribosomal protein L25-like    
                   Ribosomal protein L25-like barrel, closed; n=6, S=10; complex topology
                   2zjq  d2zjqs1  S:18-26,27-35,35-47,53-57,79-85
                   2zjr  d2zjrs1  S:18-26,27-35,35-47,53-57,79-84