proteinsbinding

Proteinsbinding, commonly referred to as protein binding or protein–protein interactions (PPIs), describes the selective physical association between two or more protein molecules or between a protein and another biological macromolecule (such as DNA, RNA, lipids, or small ligands). These interactions range from transient contacts in signaling cascades to stable assemblies in structural complexes and are central to virtually all cellular processes.

Specificity and strength of binding are determined by complementary shapes, electrostatic and hydrophobic surfaces, and hydrogen-bonding networks. Common interaction modules and motifs—such as SH2, SH3, PDZ, and leucine zippers—mediate recognition and assembly of multiprotein complexes. Binding is characterized quantitatively by affinity (Kd) and kinetics (association and dissociation rates), which influence biological outcomes.

Experimental methods used to study protein binding include X-ray crystallography, NMR spectroscopy, cryo-electron microscopy, surface plasmon resonance, isothermal titration calorimetry, yeast two-hybrid assays, and co-immunoprecipitation. Computational approaches predict interfaces and affinities using sequence, structural modeling, and network analysis; databases catalog known interactions.

Protein binding is regulated by post-translational modifications, alternative splicing, cellular localization, and competition among partners. Dysregulation or mutation of binding interfaces can cause disease, including cancers and neurodegenerative disorders, making PPIs targets for therapeutic intervention. Strategies to modulate protein binding include small molecules, peptides, and biologics designed to inhibit or stabilize specific interactions.