DNA Translation

Terms

Anticodon - The sequence of three nucleotides located on the anticodon arm of the tRNA cloverleaf structure. The anticodon bonds in antiparallel fashion with a codon of mRNA at the acceptor site of a ribosome during translation.

Small subunit - The smaller of two prokaryotic ribosomal subunits. Responsible for binding to the ribosome binding site on the mRNA.

Large subunit - The larger of the two prokaryotic ribosomal subunits. Binds after the small subunit binds to mRNA, creating the initiation complex.

Initiation complex - The prokaryotic ribosomal complex formed by the binding of the small and large subunits. Responsible for carrying out DNA translation on an mRNA strand.

Acceptor site - A three-nucleotide position in a ribosome that binds to an aminoacyl tRNA, a tRNA molecule bearing an amino acid.

Acceptor stem - One secondary structural feature of tRNA. Contains the sequence CCA and has a free 3' –OH. Binds to the amino acid.

Adenylylation - The first step in tRNA charging. Involves the "activation" of an amino acid so that the acid can be bound to a tRNA molecule. The process of activation involves the transfer of an AMP group from ATP to the amino acid.

Aminoacyl tRNA - A tRNA molecule that has been charged. It is loaded with an amino acid and is ready to participate in translation at the ribosome, where it binds to the acceptor site.

Aminoacyl-tRNA synthase - The enzyme that catalyzes the bond between specific tRNA and amino acid, to form aminoacyl tRNA.

Anticodon arm - A secondary structural feature of tRNA. Contains the anticodon that base pairs with an mRNA codon during translation.

Carboxyl group - A chemical functional group made up of a carbon double-bonded to an oxygen and single-bonded to an –OH group.

Charging - The two-step process in which an amino acid is "loaded" onto a tRNA. The first step is adenylylation; the second is the binding of tRNA and amino acid into an aminoacyl tRNA.

Charged tRNA - Term used to describe a tRNA molecule that has been loaded with an amino acid and is ready to participate in translation.

Cloverleaf - The two-dimensional structure of tRNA, resembling a cloverleaf, and caused by self-complementarity.

Dihydrouridine - One of the unusual bases found in tRNA. Contains two additional hydrogens in place of the double bond that is usually found in uracil.

Dihydrouridine arm - A secondary structural feature of tRNA. Contains a number of dihydrouridines.

Elongation factor - GTP-dependent proteins that help bring aa-tRNA to the acceptor site of a ribosome during translation. Elongation factors also help in the translocation process. Energy is supplied by the hydrolysis of GTP to GDP.

Initiation factor - Proteins that help associate pieces of the initiation complex.

Peptide bond - A carbon-nitrogen chemical bond formed between amino acid subunits of a polypeptide chain.

Peptidyl site - A three nucleotide position in a ribosome in which peptidyl tRNA is found.

Peptidyl RNA - The name given to the tRNA located in the P site of the ribosome during translation. This tRNA holds the growing polypeptide chain.

Peptidyl transferase - The enzyme responsible for catalyzing the peptide bond formation reaction between amino acids in the P site and A site of a ribosome during translation.

Polypeptide chain - A chain of many peptide, or amino acid, subunits joined together through peptide bonds.

Polyribosome - Term used to describe a group of separate ribosomes that are bound to the same mRNA strand.

Pseudouridine - One of the unusual bases found in tRNA in which the normal 1' nitrogen site of ribose attachment is switched to the 5' carbon position.

Release factor - A protein that recognizes one of three stop codons on an mRNA chain. Its binding results in the release of the completed polypeptide chain and the dissociation of the 30S and 50S subunits.

Ribosome - The structure in the cell, made up of protein and RNA (rRNA), that functions as the "factory" of protein synthesis. Ribosomes contain a binding site for mRNA, and three binding sites for tRNA: the acceptor site, the peptidyl site, and the exit site.

Ribosome binding site - An approximately 10 nucleotide sequence found in a prokaryotic mRNA strand that is recognized and bound by the ribosome. Located 5 to 11 nucleotides from the initiator codon. In eukaryotes, the ribosome binding site is functionally replaced by the 5' cap.

T arm - A secondary structural feature of tRNA. Contains the sequence thymine- pseudouridine-cytosine in its stem loop.

Translocation - The process in which the ribosome moves three nucleotides down an mRNA strand in the 3' direction. Process is catalyzed by the hydrolysis of GTP to GDP.