Can tRNA Bind Only One Amino Acid and Which Ribosomal Subunit Binds tRNA?

[max0005]

Homework Statement

Dear All,

I have a question regarding RNA translation.

Firstly, my book states that Amino-Acids are binded to tRNA through AA-Activation which is possible through ATP->AMP. The AA will then bind to the acceptor stem near 3' end. My question is:

a) Each strand of tRNA can bind only one Amino-Acid?
b) Each strand of tRNA can bind only one type of Amino-Acid?

Then, at a point it is written "The smaller subunit (of ribosomes) has the binding site for mRNA" however, a few paragraphs later, it is stated "The tRNA will bind to the base of the P site on the small subunits". Which one is correct?

Finally, it states the last stage of RNA Initiation as "The large subunit, containing the binding sites for tRNAs joins the complex". What exactly does this mean? Is it the smaller or larger subunit which binds tRNA? What complex is it joining?

Thanks in advance!

max

Homework Equations

The Attempt at a Solution

 

[Ygggdrasil]

Firstly, my book states that Amino-Acids are binded to tRNA through AA-Activation which is possible through ATP->AMP. The AA will then bind to the acceptor stem near 3' end. My question is:

a) Each strand of tRNA can bind only one Amino-Acid?
b) Each strand of tRNA can bind only one type of Amino-Acid?

Each molecule of tRNA will attach only one amino acid molecule. You will not find tRNA molecules with multiple amino acids attached (except for tRNA molecules bound by the ribosome).

Each type of tRNA molecule will attach only one type of amino acid. Alanyl-tRNAs will attach to only alanine amino acids an no other amino acids. This attachment specificity comes from the enzymes that attach amino acids to tRNAs. These enzymes will recognize specific features of the tRNA that distinguish it from other types of tRNA (e.g. the anticodon loop) and recognize specific features of the amino acid (the side chain) that distinguish it from all other types of amino acid).

Then, at a point it is written "The smaller subunit (of ribosomes) has the binding site for mRNA" however, a few paragraphs later, it is stated "The tRNA will bind to the base of the P site on the small subunits". Which one is correct?

The mRNA binds to the small subunit, then the tRNA binds to the complex formed between the small subunit and mRNA. This interaction is mainly through the anticodon loop of the tRNA binding to the mRNA, but there are other interactions between the small subunit and the tRNA.

Finally, it states the last stage of RNA Initiation as "The large subunit, containing the binding sites for tRNAs joins the complex". What exactly does this mean? Is it the smaller or larger subunit which binds tRNA? What complex is it joining?

Both the small and large subunits bind to the tRNA. They bind to different parts of the tRNA, however. The small subunit recognizes features of the tRNA near the anticodon loop and helps to ensure that the anticodon loop is correctly base-paired to the mRNA (this is to ensure that the ribosome adds the correct amino acid to the protein). The large subunit, however, recognizes features of the tRNA near the top of the tRNA where the amino acid is attached. These interactions help to catalyze peptide bond formation.

When the large subunit binds, it is binding the complex formed between the small subunit, the mRNA, the tRNA, and various initiation factors. If any of these components are missing, the large subunit will not bind to form a complete ribosome.

 

[max0005]

That was very useful! Thank you very much! :D