Which post-translational modification is observed most commonly in signal transduction?
Which post-translational modification is observed most commonly in signal transduction?
Select an option to attempt
Correct Answer: Option C
Explanation
Protein phosphorylation is the most ubiquitous and rapidly reversible post-translational modification in signal transduction. Key features: (1) Ubiquity —500 protein kinases in the human kinome; phosphorylation regulates essentially all signal transduction pathways; (2) Reversibility — kinases add phosphate (from ATP) to Ser, Thr, or Tyr; phosphatases (Ser/Thr phosphatases PP1, PP2A; Tyr phosphatases) rapidly remove it — creating an 'on/off switch'; (3) Electrostatic effects — thecharge of phosphate at pH 7 induces conformational changes and creates docking sites for SH2, PTB, BRCT domains; (4) Signal amplification — one activated kinase phosphorylates many substrates. Examples: EGFR → RAS → RAF → MEK → ERK cascade (all phosphorylation-based). Acetylation (histones, metabolic enzymes) and nitrosylation occur in signalling but are far less prevalent than phosphorylation.