Question

select all that apply

which occur during posttranslational modification?

a polyribosomal complex forms to increase the rate of synthesis.
formyl-methionine is removed from the start of the polypeptide chain.
proteins join with other proteins to form quaternary structures.
cofactors are added to proteins destined to become enzymes.
exons are spliced together.
introns are removed from the sequence.

Explanation:

Analyze the options relative to posttranslational modification

• A polyribosomal complex forms to increase the rate of synthesis: This occurs during translation (protein synthesis), not after translation.
• Formyl-methionine is removed from the start of the polypeptide chain: This is a classic posttranslational modification in prokaryotes where the initiating formyl-methionine (fMet) is enzymatically cleaved from the newly synthesized polypeptide.
• Proteins join with other proteins to form quaternary structures: This is part of protein folding and assembly into functional complexes, which is a posttranslational process.
• Cofactors are added to proteins destined to become enzymes: The attachment of cofactors, coenzymes, or prosthetic groups to form functional holoenzymes is a posttranslational modification.
• Exons are spliced together: This is a post-transcriptional modification of pre-mRNA, not a posttranslational modification of proteins.
• Introns are removed from the sequence: This is also a post-transcriptional RNA processing event.

Identify the correct choices

The events occurring during posttranslational modification are:

• Formyl-methionine is removed from the start of the polypeptide chain.
• Proteins join with other proteins to form quaternary structures.
• Cofactors are added to proteins destined to become enzymes.

Answer:

• A polyribosomal complex forms to increase the rate of synthesis.
• Formyl-methionine is removed from the start of the polypeptide chain. (Correct answer)
• Proteins join with other proteins to form quaternary structures. (Correct answer)
• Cofactors are added to proteins destined to become enzymes. (Correct answer)
• Exons are spliced together.
• Introns are removed from the sequence.