nucleotide-binding domain (NBD) of Bifidobacterium adolescentis xylulose kinase (XK) and similar proteins
The subfamily includes a group of uncharacterized proteins with similarity to xylulose kinases (XKs) from Bifidobacterium adolescentis, Streptomyces coelicolor, Actinoplanes missouriensis and Haemophilus influenzae. Members of this subfamily belong to the FGGY family of carbohydrate kinases, the monomers of which contain two large domains, which are separated by a deep cleft that forms the active site. This model includes both the N-terminal domain, which adopts a ribonuclease H-like fold, and the structurally related C-terminal domain.
Comment:catalytic residues (Asp, Thr, Asp) conserved in the FGGY family
Comment:Two Asp residues probably form a metal cofactor binding site and the second Asp residue acts as a catalytic base.
Comment:It has been proposed that the first Asp coordinates and positions the MgATP, and (in concert with the Mg2+) stabilizes the ADP leaving group during the phospho transfer. The second Asp would act as a general base during catalysis, assisting the removal of a proton from the attacking hydroxyl group. The Thr could stabilize the transition state.
Jiyao W et al.(2023). "The conserved domain database in 2023.",