Question

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Explain the regulation of the trp operon by the 5' end of the mRNA when tryptophan...

Explain the regulation of the trp operon by the 5' end of the mRNA when tryptophan is low vs high.

Expert Solution

At the 5' end of the trp Operon, there is leader sequences that regulates the translation of trp mRNA.

There are four regions of this leader sequences at 5' site of the trp operon, regions 1, 2, 3 and 4.

Region 1 contains 2 codons which codes for tryptophan. Region 2 and 3 have some complementary sequences that can form a weak loop that can be dissociated by ribosomes. Region 3 and 4 have complementary sequences that can form stron loop which cannot be dissocated by ribosomes.

When ribosomes reaches to region 1, it requires Tryptophan-tRNA as there are two trp codons.

Scenario 1 : low trp level

If there is lower amount of Tryptophan inside the cell, the migration speed of ribosomes will be lower at those two codons as trp level is low. While ribosomes take time to reach at region 2 in low trp concentration, region 2 will be free to form loop with

At the 5' end of the trp Operon, there is leader sequences that regulates the translation of trp mRNA.

There are four regions of this leader sequences at 5' site of the trp operon, regions 1, 2, 3 and 4.

Region 1 contains 2 codons which codes for tryptophan. Region 2 and 3 have some complementary sequences that can form a weak loop that can be dissociated by ribosomes. Region 3 and 4 have complementary sequences that can form stron loop which cannot be dissocated by ribosomes.

When ribosomes reaches to region 1, it requires Tryptophan-tRNA as there are two trp codons.

Scenario 1 : low trp level

If there is lower amount of Tryptophan inside the cell, the migration speed of ribosomes will be lower at those two codons as trp level is low. While ribosomes take time to reach at region 2 in low trp concentration, region 2 will be free to form loop with region 2. But this loop can be dissociated by ribosomes so translation will not be stopped

Summary : translation will not be stopped in lower level of tryptophan

region 2. But this loop can be dissociated by ribosomes so translation will not be stopped

Summary : translation will not be stopped in lower level of tryptophan

Scenario 2 : high trp level

If there is hugher level of trp, ribosome will not take much time to reach on region 2 as ribosome will reach on region 2 before formation of 2-3 loop. While region 2 is occupied by ribosomes, there will be formation of loop between regions 3 and 4 which is strong loop and cannot be dissociated by ribosomes, which results in dissociation of ribosomes from mRNA and translation will be stopped.

Summary : in higher level of trp translation will be stopped

gladiator answered 1 year ago

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