NTPbinding

NTPbinding refers to proteins and protein domains that bind nucleoside triphosphates, most commonly ATP and GTP. These interactions are central to energy transduction and signaling, and binding can regulate protein conformation, catalysis, and interactions with other molecules. NTP-binding is observed across all domains of life and in a wide range of cellular processes.

Structurally, many NTP-binding proteins belong to conserved folds that coordinate the phosphate groups of the bound NTP. The most widespread is the P-loop NTPase superfamily, typified by the Walker A motif (GxxxxGKS/T) and a Walker B motif that coordinates a magnesium ion and catalytic residues. Other NTP-binding domains use Rossmann-like folds or nucleotide-binding pockets formed by different secondary-structure arrangements. The exact motif and architecture determine whether the protein acts as an ATPase, a GTPase, or uses NTP binding primarily for substrate positioning rather than hydrolysis.

Functionally, NTP binding can drive conformational changes, assembly or disassembly of complexes, and translocation or mechanical work. Hydrolysis of NTP to NDP and inorganic phosphate often powers movement, cargo transport, or remodeling of macromolecular partners. Examples include molecular motors such as kinesins and dyneins, GTPases that regulate signaling and trafficking, helicases that unwind nucleic acids, and ABC transporters that move substrates across membranes.

In biology and bioinformatics, NTP-binding sites are common annotation targets, and conserved motifs like the Walker A/B or the P-loop are used to predict function. The term covers a broad class of proteins with diverse roles, united by their ability to bind NTPs and regulate activity through nucleotide turnover. See also NTPase, P-loop NTPase, Walker motifs, GTPase, ATPase, and ABC transporter.