Protein kinases - structure & function

The eukaryotic protein kinases are defined as enzymes that use the γ-phosphate of adenosine triphosphate (ATP) to phosphorylate serine, threonine or tyrosine residues in protein
ATP is composed of an adenine ring, ribose sugar, and three phosphate groups (triphosphate). The groups of the phosphate group are usually called the alpha (α), beta (β), and gamma (γ) phosphates.
Gamma phosphate group is the primary phosphate group on the ATP molecules that is hydrolyzed when the energy is needed to drive anabolic reactions.
Protein kinases share a similar three-dimensional catalytic domain.
The catalytic domain consists of 250 to 300 amino acids composed of a larger, generally α-helical, C-terminal subdomain and a smaller, usually β-sheet, N-terminal subdomain.
The N-and C-terminus are linked by a peptide scaffold, forming a deep groove enables the binding of the peptide substrate and an ATP molecule.
The ATP-binding region rotates into "on" and "off" conformations depending on ATP binding and the activation state of the enzyme
Protein kinases are classified into five major groups according to the amino acid residue that they phosphorylate, including
serine/threonine protein kinases (ST-PKs),
tyrosine protein kinases (TKs),
histidine-specific kinases,
dual-specificity protein kinases, and
aspartic acid/glutamic acid-specific protein kinases.