- A: a/b three-layered sandwiches
- X: Nucleoside phosphorylase/phosphoribosyltransferase catalytic domain
- H: Nucleoside phosphorylase/phosphoribosyltransferase catalytic domain
- T: Nucleoside phosphorylase/phosphoribosyltransferase catalytic domain
- F: Glycos_transf_3