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Test: Biochemistry
Receptor tyrosine kinases (RTKs) transduce extracellular signals into intracellular signaling cascades. This is possible because RTKs have an extracellular ligand binding domain to sense ligands outside of the cell, a transmembrane domain that spans the cell membrane, and an intracellular domain that activates pathways within the cell.
| 1. | Which of the following best describes the mechanism by which the cytosolic domains of RTKs activate downstream signaling cascades? |
Ligand binding to the extracellular RTK domain stimulates dimerization of RTKs, and the cytosolic domains cross-phosphorylate one another to activate the kinase domains.
Ligand binding to the extracellular RTK domain triggers an influx of calcium through calcium-channels, activating second messengers within the cell.
Ligand binding to the extracellular RTK domain permits the RTK to interact with other receptors on other cells, triggering bidirectional signaling cascades.
Ligand binding to the extracellular RTK domain triggers cleavage of the intracellular domains, which then act as soluble second messengers to activate protein kinases.
Ligand binding to the extracellular RTK domain facilitates phosphorylation of the RTK intracellular domain by protein kinase A, which is required for all downstream signaling cascades to be activated.
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