Lecture 6 - Control at translation

Question 1

What is a monogenic (monocistronic) mRNA

Answer 1

Only in prokaryotic cells

Ability to translate after transcribe.
Done via. H2N-Met, first AUG from 5’ end

Question 2

Where is the shine-delgarno sequence found?

Answer 2

Upstream of AUG

Question 3

What is polarity?

Answer 3

The binding of weak and strong ribosomes.

If coding regions are close to each other, the ribosome can track along the mRNA. But coding regions are distant, they have to dissociate.

mRNA may not be linear (secondary structure) affecting access of ribosomes to shine-delgarno sequence and initiator AUG or interfere with progress of ribosomes along the message

Question 4

What is the R17 coat protein?

Answer 4

Translational repressor

Targers R17 replicase, hairpin that includes ribosomes binding site

Question 5

What is T4 RegA?

Answer 5

Translational repressor

early T4 mRNAs, various sequences including initiation codon

Question 6

What is T4 DNA polymerase?

Answer 6

Translational repressor

Targets T4 DNA polymerase, Shine-Dalgarno sequence

Question 7

What is T4 p32?

Answer 7

Translational repressor

Targets gene 32, single stranded 5’ leader

Question 8

Outline ribosome structure

Answer 8

70s ribosome

50s ribosomal subunit + 30s ribsosomal subunit

rProteins and rRNA’s must all be mode in correct proportions

Ribosomes are 40% growing bacteria cell (dry)

Question 9

What is autogenous control?

Answer 9

When a protein binds to its own mRNA and prevents its own translation. Titration effect

Question 10

What is the Stringent response?

Answer 10

When bacteria are starved so that amino acids are in short supply, an alarm molecule called ppGpp is synthesized.

GTP+ATP -> (p)ppGpp + AMP

Made by stringent factor (relA)

This ppGpp alters the promoter specificity of RNA Polymerase to REDUCE TRANSCRIPTION coding for rRNAs

Question 11

How is the translation of mRNAs for rProteins shut down?

Answer 11

Autogenous control