This domain is found across all species from bacteria to human, and the function was determined first in a hyperthermophilic bacterium to be an NTPase [1]. The structure of one member-sequence represents a variation of the RecA fold, and implies that the function might be that of a DNA/RNA modifying enzyme [2]. The sequence carries both a Walker A and Walker B motif which together are characteristic of ATPases or GTPases. The protein exhibits an increased expression profile in human liver cholangiocarcinoma when compared to normal tissue [3].

1: Thermophile-specific proteins: the gene product of aq_1292 from Aquifex aeolicus is an NTPase. Klinger C, Rossbach M, Howe R, Kaufmann M; BMC Biochem. 2003;4:12. PMID:14503925

2: Crystal structure of THEP1 from the hyperthermophile Aquifex aeolicus: a variation of the RecA fold. Rossbach M, Daumke O, Klinger C, Wittinghofer A, Kaufmann M; BMC Struct Biol. 2005;5:7. PMID:15777481

3: NMR structure and functional characterization of a human cancer-related nucleoside triphosphatase. Placzek WJ, Almeida MS, Wuthrich K; J Mol Biol. 2007;367:788-801. PMID:17291528