Which of the following is required for post-translational modification?
**Core Concept**
Post-translational modification (PTM) refers to the series of processes that proteins undergo after translation to modify their structure, function, and localization. These modifications can significantly affect protein activity, stability, and interactions.
**Why the Correct Answer is Right**
The correct answer is **C. Enzymes**. Enzymes play a crucial role in post-translational modification by catalyzing specific reactions that alter the protein's primary, secondary, or tertiary structure. Examples of enzymes involved in PTM include protein kinases (phosphorylation), proteases (proteolytic cleavage), and glycosyltransferases (glycosylation). These enzymes recognize specific amino acid sequences or structural motifs on the target protein, enabling precise modification.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because nucleic acids (DNA and RNA) are involved in the synthesis of proteins, not their post-translational modification.
**Option B:** Incorrect because receptors are not directly involved in PTM; they often interact with modified proteins, however.
**Clinical Pearl / High-Yield Fact**
PTMs are essential for regulating protein function, and dysregulation of these processes can lead to various diseases, including cancer, diabetes, and neurodegenerative disorders. For example, the PTM of tau protein is a hallmark of Alzheimer's disease.
**Correct Answer:** C. Enzymes