ATPbinding

ATP binding refers to the reversible interaction of a protein or other molecule with adenosine triphosphate (ATP). Binding is often reversible and can position ATP for hydrolysis, phosphate transfer, or regulatory control. In cells, ATP binding is central to energy metabolism, signaling, and catalysis.

Many proteins possess conserved ATP-binding motifs. P-loop NTPases carry a Walker A motif (GxxxxGKT/S) and a Walker B motif; nucleotide-binding domains in ABC transporters form ATP-binding cassettes and dimerize on ATP binding. Protein kinases bind ATP in their active sites to donate phosphate groups to substrates. Other systems, such as actin, myosin, DNA helicases, and chaperones like GroEL, also bind ATP as part of their function.

ATP binding can regulate conformation and activity; in motor proteins, binding and hydrolysis drive movement; in transporters, binding of ATP promotes substrate translocation by conformational change. Some proteins bind ATP without immediate hydrolysis, acting as regulatory subunits or allosteric effectors.

Study and characterization: binding affinity (Kd) and thermodynamics are measured by ITC; kinetics by SPR or fluorescence; structural studies by X-ray crystallography or NMR reveal binding geometry; mutagenesis identifies key residues. Pathways and inhibitors target ATP-binding pockets in disease contexts, such as kinases in cancer or ABC transporters in multidrug resistance.