Lineage for Family c.23.16.5: A4 beta-galactosidase middle domain

1. Root: SCOP 1.73

2. Class c: Alpha and beta proteins (a/b) [51349] (141 folds)

3. Fold c.23: Flavodoxin-like [52171] (15 superfamilies) 3 layers, a/b/a; parallel beta-sheet of 5 strand, order 21345

4. Superfamily c.23.16: Class I glutamine amidotransferase-like [52317] (8 families) conserved positions of the oxyanion hole and catalytic nucleophile; different constituent families contain different additional structures

5. Family c.23.16.5: A4 beta-galactosidase middle domain [82351] (1 protein) probable non-catalytic branch of the class I GAT family; overall fold is very similar but the active site is not conserved