Question

1.What is the role of histone acetylation in eukaryotic cells?

2.What is the role of amino-acyl-tRNA-synthetases?

Answer 1

ANSWER 1] ROLE OF HISTONE ACETYLATION IN EUKARYOTIC CELLS.

Acetylation: As the name suggests, acetylation is the process in which an acetyl functional group is added to a chemical compoud.

Histone: Histones are a group of protein that pack DNA togheter to form nucleosomes. They are positively charged and DNA is negatively charged. Hence, they pack up together.

Histone acetylation: Addition of acetyl group to the histone tail (i.e., to the amino acid Lysine)

Catalyst: Histone acetyltransferase(HAT)

Role of histone acetylation: The main role of histone acetylation is to make DNA transcription ready.

• Acetylation of histone removes the positive charge on it.
• This reduces the affinity of hitones for the negatively charged DNA.
• As a result the packed nucleosome and chromatin fibres loosen up.
• Thus, this makes the DNA active for transcription.

Hence, histone acetylation plays a key role in gene activation by making DNA ready for transcription.

ANSWER 2] ROLE OF AMINO- ACYL- tRNA- SYNTHETASES.

Amino- acyl- tRNA- syntyetase is an enzyme useful in protein synthesis, especially in RNA translation. It is also called as tRNA ligase.

The main role of this enzyme is to catalyze aminoacylation of tRNA, that is, to attach a given amino acid onto its tRNA.

• It is a two step process.
• The first step is "Activation" that is formation of aminoacyl - AMP by the hydrolysis of ATP.
• The second step is "Transfer". In this step the aminoacyl- AMP binds to the appropriate tRNA and the amino acid is transferred to tRNA forming aminoacyl tRNA and AMP as two products.

This enzyme also does editing of molecules if an incorrect amino acid gets attached to the tRNA. If this happens then the hydrolysis of aminoacyl tRNA takes place.