Protein kinase receptors are characterized by

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Protein kinase receptors are characterized by

Protein kinase receptors work by spanning the cell membrane and bringing their catalytic activity inside the cell. They have an extracellular domain that binds ligands, a single transmembrane segment, and a cytoplasmic kinase domain that can autophosphorylate and phosphorylate other proteins when activated. This combination—being a membrane-spanning protein with an internal kinase enzyme—is the defining feature. When a ligand binds, these receptors often form dimers and their kinase domains phosphorylate themselves and nearby proteins, creating docking sites that start signaling cascades inside the cell. The other options describe different types of receptors: ones that move to the nucleus to bind DNA; intracellular receptors lacking a membrane span; or receptors that always activate G proteins directly, which is characteristic of G protein–coupled receptors rather than protein kinase receptors.

Protein kinase receptors work by spanning the cell membrane and bringing their catalytic activity inside the cell. They have an extracellular domain that binds ligands, a single transmembrane segment, and a cytoplasmic kinase domain that can autophosphorylate and phosphorylate other proteins when activated. This combination—being a membrane-spanning protein with an internal kinase enzyme—is the defining feature. When a ligand binds, these receptors often form dimers and their kinase domains phosphorylate themselves and nearby proteins, creating docking sites that start signaling cascades inside the cell. The other options describe different types of receptors: ones that move to the nucleus to bind DNA; intracellular receptors lacking a membrane span; or receptors that always activate G proteins directly, which is characteristic of G protein–coupled receptors rather than protein kinase receptors.

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