This domain is found in competence-induced protein A (CinA) present in Thermus thermophiles. CinA is important in the horizontal transfer of genes via competence and may also participate in the pyridine nucleotide cycle, which recycles products formed by non-redox uses of NAD. This domain has a KH-type fold and contains the absolutely conserved Glu-187, which stabilizes the binding of Mg2+ and hence polarizes the P=O bond for hydrolysis. A major feature of the CinA in T. thermophiles structure is the asymmetry in the dimer, which is caused by contact between a KH-type domain on the opposite chain and the bound ADP-ribose. This has the effect of closing the active site, allowing additional recognition of ADP-ribose by residues from the KH-type domain [1].

1: Structure and mechanism of the bifunctional CinA enzyme from Thermus thermophilus. Karuppiah V, Thistlethwaite A, Dajani R, Warwicker J, Derrick JP; J Biol Chem. 2014;289:33187-33197. PMID:25313401