3.4 - Translation Flashcards
What is the function of aminoacyl tRNA synthetase enzymes and why are they are described as “the translators” of the genetic information?
An aminoacyl-tRNA synthetase is an enzyme that attaches the appropriate amino acid onto its corresponding tRNA. It does so by catalyzing the transesterification of a specific cognate amino acid or its precursor to one of all its compatible cognate tRNAs to form an aminoacyl-tRNA.
This is also called “charging” the tRNA with an amino acid. Once the tRNA is charged, a ribosome can transfer the amino acid from the tRNA onto a growing peptide, according to the genetic code. Aminoacyl tRNA therefore plays an important role in RNA translation, the expression of genes to create proteins.
Further reading: Synthetase first binds to ATP and the corresponding amino acid to form aminoacyl-adenosine, releasing inorganic pyrophosphate. The adenylate-aRS complex then binds to the D arm of the appropriate tRNA molecule and the amino acid is transferred from aa-AMP to the 2’- or 3’-OH of the last tRNA nucleotide at the 3’ end.
Source: Delarue, M (1995). “Aminoacyl-tRNA synthetases”. Structural Biology.
Further reading:
Why does Wobble effect occur?
The 16S RNA in the 30S ribosomal subunit possesses a means of examining whether the standard Watson-Crick base pairs have formed between the 1st codon base and the 3rd anticodon base, as well as between the 2nd codon base and the 2nd anticodon base. However, there is no system to check whether the 3rd codon base and the 1st anticodon base are complimentary to one another and this amounts to the more lenient base-pairing that is witnessed exclusively at the 3rd position.
Source: Berg J., Tymoczko J and Stryer L. (2007) Biochemistry, 6th edition, New York: WH Freeman.
What are the features of the genetic code?
The genetic code is universal: All known living organisms use the same genetic code.
The genetic code is non-overlapping: Each codon codes for just one amino acid.
The genetic code is redundant: Most amino acids are encoded by more than one codon.
What RNAs involved in the process of translation and what are their roles?
mRNA is translated into protein by the joint action of tRNA and the ribosome, which is composed of numerous proteins and two major rRNA molecules.
What are the roles of the ribosome binding sites (RBS)?
RBS is a sequence of nucleotides upstream of the start codon of an mRNA transcript that is responsible for the recruitment of a ribosome during the initiation of translation.
Three tRNA-binding sites are located on the ribosome, termed the A, P and E sites.
What is the “wobble” effect in tRNA binding?
The Wobble effect is that the 3rd base in an mRNA codon can undergo non-Watson-Crick base pairing with the 1st base of a tRNA anticodon.
If A is at the 3rd position in the codon it can base pair with U or I.
If U is at the 3rd position in the codon it can base pair with A, G or I.
If G is at the 3rd position in the codon it can base pair with C or U.
If C is at the 3rd position in the codon it can base pair with G or I.
