A 55-year-old man undergoes molecular profiling of a pancreatic adenocarcinoma. Sequencing reveals a point mutation in a proto-oncogene that encodes a small monomeric GTP-binding protein. The mutant protein retains GTP binding but has markedly reduced intrinsic GTPase activity. Which protein is mutated?
- A JAK2
- B RAS ✓
- C SRC
- D MYC
Correct answer: B. RAS
Explanation
RAS is a small monomeric GTP-binding signal transducer that is active in the GTP-bound state. Mutant RAS loses GTPase activity and cannot be switched off by GAPs, so it signals growth continuously. JAK2 is a tyrosine kinase linked to cytokine receptors, SRC is a non-receptor tyrosine kinase, and MYC is a nuclear transcription factor, none of which bind GTP.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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