Translation of RNA to Protein

Proteins have a linear primary sequence of no more than 20 encoded amino acids and this underlying simplicity is used to express great subtlety in structure and versatility in function. For these reasons, proteins are essential to the structure and function of living cells. The assembly of polypeptide chains from amino acids and their subsequent modifications, leading to the final three-dimensional protein structure, are exceptionally complex processes; many components are involved and much of the cell's energy is utilized. Each peptide bond requires the expenditure of four high-energy phosphate bonds (ATP is converted to AMP and two molecules of GTP are converted to GDP). This value excludes the energy used for initiation and release of the polypeptide chains and the cost of synthesizing and processing mRNA. The linear amino acid sequence of a protein is encoded within the gene as a linear deoxyribonucleotide sequence. Early steps in the biosynthesis of a protein include transcription of the gene and appropriate processing of the transcript leading to the production of mature messenger RNA (mRNA). We describe the mechanisms involved in translating mRNA to produce a polypeptide chain which has the amino acid sequence specified by the gene. Translation takes place after mRNA is bound to small ribonucleoprotein particles called ribosomes through the mediation of aminoacyl tRNA which links the linear nucleotide sequence of mRNA with the linear amino acid sequence of the encoded polypeptide. The genetic message is read sequentially as mRNA moves relative to the ribosome. Thus, the polypeptide chain is formed by the sequential incorporation of amino acids into peptide linkage. The process of translation is achieved with high fidelity with less than one error per 10 000 amino acids incorporated into protein. The mechanisms of protein synthesis are essentially the same for all cells irrespective of whether they have a nucleus (eukaryotes) or not (prokaryotes). Keywords: Anticodon; Antiparallel Base pairing; Codon; Elongation; Fidelity; Initiation; Polarity; Reading Frame; Template Strand; Termination; Translation; Translocation