Teacher:Given a scientific passage and an answer, generate a question for the given answer.
Teacher: Now, understand the problem? Solve this instance: Passage: Receptor tyrosine kinases epidermal growth factor receptor (EGFR), platelet-derived growth factor receptor (PDGFR), vascular endothelial growth factor receptor (VEGFR), HER2/neu Receptor tyrosine kinases add phosphate groups to other proteins to activate or inactivate them. Receptor kinases add phosphate groups to receptor proteins at the surface of the cell. These receptor proteins receive signals from outside the cell and initiate a signal transduction process inside the cell. Tyrosine kinases add phosphate groups to tyrosine residues in the target protein. They can cause cancer by turning the receptor permanently on (constitutively), even without signals from outside the cell. Answer: receptor kinases
Student:
What adds phosphate groups to receptor proteins at the surface of the cell?