Comparison of the active site of GTFA-ΔN (blue, catalytic domain A; green, domain B) and GTF180-ΔN. Relevant residues from GTFA-ΔN are shown with blue or green C atoms and black labels and residues from GTF180-ΔN are shown with white C atoms and grey labels. (a) Superposition of GTFA-ΔN with the GTF180-ΔN D1025N–sucrose complex (subsites −1 and +1; PDB entry 3hz3
; Vujičić-Žagar et al., 2010). The three catalytic residues and the tyrosine residue below subsite −1 are shown in stick representation. The sucrose bound to GTF180-ΔN is shown with yellow C atoms. (b) Superposition of GTFA-ΔN with the GTF180-ΔN–maltose complex (subsites +1 and +2; PDB entry 3kll
; Vujičić-Žagar et al., 2010). Maltose from the GTF180-ΔN complex, with its reducing-end glucosyl unit (subsite +2) stacking with a conserved tryptophan residue, is shown with yellow C atoms. The O1 atom of the acceptor sugar residue, which possibly interacts with Asn1134 in GTFA-ΔN, is indicated with an asterisk (*).