This domain is found at the C-terminal end of Pyrimidine/purine nucleotide 5'-monophosphate nucleosidase from Escherichia coli (PpnN, also known as YgdH) and similar proteins mainly found in gammaproteobacteria. PpnN is a nucleosidase that catalyzes the hydrolyzis of the N-glycosidic bond of diverse pyrimidine and purine nucleotide 5'-monophosphates. The binding of (p)ppGpp, an alarmone molecule that plays a role in the bacterial stringent response, gives rise to a large conformational change in the terminal region that leads to the exposure of the catalytic pocket. This domain shows a completely alpha-helical fold with an extension that wraps around the central domain.
Jiyao W et al.(2023). "The conserved domain database in 2023.",