Molecular biology and genetics: eIF2 phosphorylation in reticulocytes: practice question

A Biochemistry question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Biochemistry · Molecular biology and genetics: eIF2 phosphorylation in reticulocytes

Sample item

In haem-deficient reticulocytes, globin synthesis stops because the haem-regulated inhibitor kinase becomes active. Which initiation factor does it phosphorylate?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. eIF2

Phosphorylation of the alpha subunit of eIF2 prevents recycling of GDP to GTP by eIF2B, so Met-tRNA cannot be delivered to the ribosome and initiation stops. This couples globin synthesis to haem availability. Other stress kinases use the same mechanism.

Option by option

  • A. eEF2

    eEF2 mediates translocation and is the target of diphtheria toxin.

  • B. EF-Tu

    EF-Tu is a bacterial elongation factor.

  • C. eIF4E

    eIF4E binds the mRNA cap and is regulated by 4E-binding proteins.

  • D. eIF2 (correct)

    Correct. Phosphorylated eIF2 blocks initiator tRNA delivery and shuts down translation.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is D, eIF2. Phosphorylation of the alpha subunit of eIF2 prevents recycling of GDP to GTP by eIF2B, so Met-tRNA cannot be delivered to the ribosome and initiation stops.

Why is "eEF2" not the answer?

eEF2 mediates translocation and is the target of diphtheria toxin.

Why is "EF-Tu" not the answer?

EF-Tu is a bacterial elongation factor.

Why is "eIF4E" not the answer?

eIF4E binds the mRNA cap and is regulated by 4E-binding proteins.

What concept does this question test?

It tests Molecular biology and genetics: eIF2 phosphorylation in reticulocytes in Biochemistry. This couples globin synthesis to haem availability. Other stress kinases use the same mechanism.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Molecular biology and genetics: eIF2 phosphorylation in reticulocytes?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.