If a protein is slightly misfolded, it could be because of

Question

BlackTom AI · Accepted Answer

We begin by restating the question and listing all answer choices to ensure clarity before evaluating each option.
Question: If a protein is slightly misfolded, it could be because of
Options:
1) a mutation causing a change to an amino acid.
2) the mRNA was accidentally read backwards by the ribosome.
3) processing occurring in the cytoplasm instead of the endoplasmic reticulum.
4) a deletion mutation causing one nucleotide to be lost.

Now, let's analyze each option one by one.

Option 1: a mutation causing a change to an amino acid.
- Rationale: A missense mutation alters a codon so that a different amino acid is incorporated into the growing polypeptide. This change can disrupt local folding, alter side-chain interactions, and destabilize the folded structure, potentially causing slight misfolding. This is a plausible molecular basis for misfolding because even a single amino acid substitution can perturb hydrophobic cores, salt bridges, or hydrogen-bond networks essential for proper folding.

Option 2: the mRNA was accidentally read backwards by the ribosome.
- Rationale: If the ribosome were to read mRNA in reverse, translation would produce a completely different and likely nonfunctional peptide, not a mildly misfolded version of the intended protein. In addition, the ribosome uses codon-anticodon recognition to ensure correct reading frames; reverse reading would disrupt the entire sequence rather than cause a subtle misfolding. This scenario is biologically implausible under normal cellular conditions and would not explain a slight conformational defect of the correctly encoded protein.

Option 3: processing occurring in the cytoplasm instead of the endoplasmic reticulum.
- Rationale: For many secreted or membrane-associated proteins, folding and processing occur in the endoplasmic reticulum (ER) because the ER provides the oxidative environment, chaperones, and disulfide bond formation machinery needed for proper maturation. If such proteins were processed in the cytoplasm instead, the folding environment could differ markedly, potentially leading to misfolding. However, this option implies a specific trafficking/processing error for proteins typically targeted to the ER; while plausible for certain proteins, not all misfoldings arise from where processing occurs, and not all proteins require ER processing. It is a possible contributor in some contexts but not universally applicable as a general cause of slight misfolding.

Option 4: a deletion mutation causing one nucleotide to be lost.
- Rationale: A single-nucleotide deletion typically causes a frameshift, altering the downstream amino acid sequence and often resulting in a truncated or drastically misfolded protein. This would more likely produce a severely misfolded or nonfunctional protein rather than a mild, just slightly misfolded state. While frameshift-induced misfolding is possible, the description of a single nucleotide deletion usually leads to substantial, not subtle, conformational disruption.

In summary, each option presents a different mechanism, with varying likelihoods and implications for protein folding. The missense mutation (Option 1) directly changes an amino acid and can subtly perturb folding without necessarily destroying the entire protein, making it a plausible cause of slight misfolding. The other options describe scenarios that either propose improbable molecular events (reverse-read of mRNA), context-dependent processing issues that may or may not apply depending on protein type (ER vs cytoplasm processing), or typically produce more drastic disruption (frameshift from a deletion).

AGRI10050_2025_SM1 Mega progress quiz Part 1 (W2-W4)

If a protein is slightly misfolded, it could be because of

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