The Role of Trna in Protein Synthesis

The Role of tRNA in Protein Synthesis

Transfer RNAs play the central role in translation. They are the adaptor molecules, whose existence was predicted by Francis Crick in 1956 (Crick, 1990), which form the link between the mRNA and the polypeptide that is being synthesized. This is both a physical link, tRNAs binding to both the mRNA and the growing polypeptide, and an informational link, tRNAs ensuring that the polypeptide being synthesized has the amino acid sequence that is denoted, via the genetic code, by the sequence of nucleotides in the mRNA. To understand how tRNAs play this dual role we must examine aminoacylation, the process by which the correct amino acid is attached to each tRNA, and codon-anticodon recognition, the interaction between tRNA and mRNA.

Messenger RNA (mRNA)

Messenger RNA is RNA that carries information from DNA to the ribosome sites of protein synthesis in the cell. Once mRNA has been transcribed from DNA, it is exported from the nucleus into the cytoplasm (in eukaryotes mRNA is "processed" before being exported), where it is bound to ribosomes and translated into protein. After a certain amount of time the message degrades into its component nucleotides, usually with the assistance of RNases.

The ribosomes plays a very important role in protein synthesis, which is the process by which proteins are made from individual amino acids. Without the ribosomes the message would not be read, thus proteins could not be produced. Therefore, ribosomes play a very important role in role in protein synthesis. The primary agent in the process of translating the mRNA into a specific amino acid chain is the ribosome, which consists of two subunits. These subunits are made up of a third and extremely abundant type of RNA, ribosomal RNA (rRNA), and together contain up to eighty-two specific proteins assembled in a precise sequence Label. The ribosomes constituents must be put together in an extremely precise position and sequence. This assembled ribosome displays a series of small groves, tunnels, and platforms, where the action of protein synthesis occurs Label. There are the active sites, each dedicated to one of the tasks required for translation of mRNA into protein. Proteins being synthesized for export out of the cell, are made by ribosomes attached to the rough endoplasmic reticulum. In contrast, proteins for use by the cell are generally made in the cytoplasm by free ribosomes. Several of these free ribosomes may attach to a single mRNA molecule, giving rise to the polyribosome or polysome Label. Protein synthesis takes place on polyribosomes (or polysomes) where 80S ribosomes associate with an mRNA coding for a given protein. The number of ribosomes associated in the polysomal chains depends on the size of the mRNA. This is also associated with the size of the protein that is being synthesized. Outside the polyribosome, the ribosomes are dissociated and form a pool of free subunits. Transfer RNAs are also bound to the ribosome. There are quite a few factors involved in the formation of the initiation complex. These include: GTP, methionine tRNA, an initiation codon in mRNA, 80S ribosomes, and three protein factors Label. The process of protein synthesis begins with the