Question

What is the name of the proteins that catalyze the release of the peptide chain at translation termination?

Question 10 options:

	1) Terminators
	2) Releasors
	3) Rho
	4) Release factors

Answer 1

Answer: 4) Release factor

Explanation:

Termination of translation occurs when one of the three termination codon moves into the A site.

Theses factors are recognized in E.coli by release of release factors: RF1, which recognizes UGA and UAA. The binding of these release factors results in hydrolysis of the bond linking to the peptide to the t-RNA at the P site.

Termination of Protein Synthesis:

• Releasing factor helps in the termination.
• Stop codon is in the A site.
• Releasing factor-1 (RF-1) recognizes the stop codon in the A-site.
• RF-1 is bound by RF-3 and GTP.
• This complex with peptidyl transferase promotes the hydrolysis bond between the chain and tRNA.

• This involves hydrolysis of GTP to GDP.

Rho factor:

Chain termination in transcription and RNAP release:

By two methods:

• r (rho) factor-dependent termination

The termination signal for transcription in the template strand is identified by r factor.

r factor is an ATP dependent RNA-DNA helicase that disrupts the nascent RNA-DNA complex.

• Intrinsic (Spontaneous) or r (rho) factor independent termination.

RNA polymerase identifies the termination signal on the template strand without the aid of r factor.

But for this termination the nascent RNA should have certain pre-requisites.

1. GC rich region that forms a hairpin turn

2. U rich region after the GC rich region. The binding of A-U is weak, hence, facilitate termination of transcription.