InterPro domain: IPR027417

The P-loop NTPase fold is the most prevalent domain of the several distinctnucleotide-binding protein folds.

The most common reaction catalysed by enzymes of the P-loop NTPase fold is the hydrolysis of the beta-gamma phosphate bond of a bound nucleoside triphosphate (NTP). The energy from NTP hydrolysis is typically utilised to induce conformational changes in other molecules, which constitutes the basis of the biological functions of most P-loop NTPases. P-loop NTPases show substantial substrate preference for either ATP or GTP [ 1 ].

P-loop NTPases are characterised by two conserved sequence signatures, theWalker A motif (the P-loop proper) and Walker B motifs which bind, respectively, the beta and gamma phosphate moieties of the bound NTP, and a Mg2+ cation [ 2 ].

P-loop ATPase domains belong to one of the two major divisions. The kinase-GTPase (KG) division includes the kinases and GTPases, and the ASCE division, characterised by an additional strand in the core sheet, which is locatedbetween the P-loop strand and the Walker B strand. Most members of the ASCE division utilise ATP and members of this group include AAA+, ABC, PilT, HerA-FtsK, superfamily 1/2 (SF1/2) helicases, and the RecA/ATP-synthase superfamilies of ATPases, etc [ 3 , 4 ].

1. STAND, a class of P-loop NTPases including animal and plant regulators of programmed cell death: multiple, complex domain architectures, unusual phyletic patterns, and evolution by horizontal gene transfer. J. Mol. Biol. 343, 1-28
2. Distantly related sequences in the alpha- and beta-subunits of ATP synthase, myosin, kinases and other ATP-requiring enzymes and a common nucleotide binding fold. EMBO J. 1, 945-51
3. Classification and evolution of P-loop GTPases and related ATPases. J. Mol. Biol. 317, 41-72
4. Evolution and classification of P-loop kinases and related proteins. J. Mol. Biol. 333, 781-815