autophosphorylaation

Autophosphorylation is the process by which a protein kinase transfers a phosphate group from ATP to a residue on itself, thereby modulating its activity. The reaction can occur in two forms: cis autophosphorylation, where the kinase domain phosphorylates its own activation loop or other sites within the same polypeptide; and trans autophosphorylation, where one kinase subunit phosphorylates a neighboring subunit in a dimer or oligomer.

In many receptor tyrosine kinases, ligand-induced dimerization promotes trans-autophosphorylation of tyrosine residues in the activation loop or other cytoplasmic tails, increasing catalytic activity and creating binding sites for signaling proteins via SH2 or PTB domains. Autophosphorylation also occurs in non-receptor protein tyrosine kinases (e.g., Src family) and serine/threonine kinases, where phosphorylation of serine or threonine residues can modulate activity.

In bacteria and archaea, histidine kinases autophosphorylate on histidine residues, transferring the phosphate to aspartate on response regulators as part of two-component signaling. The term thus spans diverse systems that regulate cellular processes through self-catalyzed phosphorylation.

The functional consequences of autophosphorylation include altered enzyme kinetics, changes in substrate specificity, and assembly of signaling complexes. Dysregulation can contribute to disease, notably cancer, and autophosphorylation is a common target for pharmacological intervention. Detection methods include phosphorylation-specific antibodies and mass spectrometry.