Protein synthesis

Protein synthesis

Protein synthesis is the creation of proteins using DNA and RNA.For synthesis of protein, a succession of tRNA molecules charged with their appropiate amino acids have to be brought together with an mRNA molecule and matched up by base-pairing through their anticodons with each of its successive codons. The amino acids then have to be linked together to extend the growing protein chain, and the tRNAs, relieved of their burdens, have to be released. This whole complex of processes is carried out by a giant multimolecular machine, the ribosome, formed of two main chains of RNA, called ribosomal RNA (rRNA), and more than 50 different proteins. This evolutionarily ancient molecular juggernaut latches onto the end of an mRNA molecule and then trundles along it, capturing loaded tRNA molecules and stitching together the amino acids they carry to form a new protein chain. [Alberts, Bruce. Molecular Biology of the Cell, 5e. New York: Garland Science, 2008. ]

Process

Transcription -Protein synthesis starts in the nucleus, where the DNA is held. DNA structure is two chains of sugars and phosphates joined by pairs of nucleic acids; Adenine, Guanine, Cytosine, and Thymine. Similar to DNA replication, the DNA is "unzipped" by the enzyme helicase, leaving the single nucleotide chain open to be copied. RNA polymerase reads the DNA strand, and synthesizes a single strand of messenger RNA (mRNA). This single strand of mRNA leaves the nucleus through nuclear pores, and migrates into the cytoplasm where it joins with ribosomes.Where protein synthesis occurs by the formation of amino acids.
*Note: in the new RNA strand, the nucleotide Uracil takes the place of Thymine.

Translation - the process of converting the mRNA codon sequences into an amino acid polypeptide chain.

1. Initiation - A ribosome attaches to the mRNA and starts to code at the FMet codon (usually AUG, sometimes GUG or UUG).

2. Elongation - tRNA brings the corresponding amino acid to each codon as the ribosome moves down the mRNA strand.

3. Termination - Reading of the final mRNA codon (aka the STOP codon), which ends the synthesis of the peptide chain and releases it.

Notes

Biological and artificial methods for creation of proteins differ significantly.
*For biological protein synthesis, see protein biosynthesis
*For artificial protein synthesis, see peptide synthesis


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