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Joined 2026-09-21 Message
Incoming links: Protein kinase
Autophosphorylation 2026-10-13
Autophosphorylation is phosphorylation of a protein kinase by its own catalytic activity or that of another member of the same protein kinase assembly. Distinguish modification within one chain from trans-autophosphorylation between partners.
Protein kinase 2026-10-13
A protein kinase is an enzyme that catalyzes phosphorylation of a protein. In receptor tyrosine kinase signaling, ATP supplies the transferred phosphate group.
Protein phosphatase 2026-10-13
A protein phosphatase is an enzyme that removes a phosphate group from a modified protein through hydrolysis. This restores a modifiable site rather than regenerating ATP by simply running protein kinase chemistry backward.
Receptor tyrosine kinase 2026-10-14
A receptor tyrosine kinase combines extracellular ligand recognition with an intracellular protein kinase protein domain. A membrane-spanning segment connects these parts across the cell membrane: the signal changes the intracellular machinery without requiring the ligand to enter the cytosol. The protein kinase transfers a phosphate group from ATP to selected tyrosine residues on proteins, including the receptor itself.[ref]
Signaling through Enzyme-Linked Cell-Surface Receptors. “Activated Receptor Tyrosine Kinases Phosphorylate Themselves”: extracellular binding, intracellular catalytic domains and ATP-dependent phosphate transfer
This architecture makes a reception event useful in two ways: it can change catalytic activity and assemble a local group of signaling proteins. Trans-autophosphorylation can create phosphotyrosine residues recognized by SH2 domains. Recruitment positions a downstream enzyme or relay protein near its partners. Neither every modified site nor every recruited protein has the same effect; association is a specific molecular connection, rather than a universal command to activate everything nearby.[ref]
Signaling through Enzyme-Linked Cell-Surface Receptors. “Phosphorylated Tyrosines Serve as Docking Sites For Proteins With SH2 Domains”, Figure 15-53: signaling enzymes, adaptors and negative regulators
Compare the epidermal growth factor receptor with the insulin receptor. Their common topology does not impose one activation geometry or make assembly equivalent to activity. The receptor phosphorylation assay consequently needs more than evidence that two protein chains associate.
Receptor tyrosine kinase architecture and distinct activation mechanisms
. Original topology cartoons contrasting EGFR with the preassembled insulin receptor. Orange dots mark phosphotyrosine residues; S–S marks protein disulfide bonds. The EGFR panel separates asymmetric catalytic contact from partner-tail phosphorylation. Shapes, distances and drawn ligand counts are explanatory, rather than atomic structures or binding stoichiometry. Details.
Trans-autophosphorylation 2026-10-13
In trans-autophosphorylation, one protein kinase chain phosphorylates another partner chain. “Auto” therefore does not require the modified site and catalytic active site to be on the same chain. The insulin receptor provides an activation-loop example; EGFR shows why autophosphorylation and catalytic activation need not be the same event.