Protein biosynthesis 24553 215147852 2008-05-26T22:35:43Z ClockworkSoul 137964 Reverted edits by [[Special:Contributions/Johannesvillavelius|Johannesvillavelius]] ([[User talk:Johannesvillavelius|talk]]) to last version by 18.51.6.159 {{Unreferenced|date=December 2007}} '''Protein biosynthesis''' (synthesis) is the process in which [[cell (biology)|cells]] build [[protein]]s. The term is sometimes used to refer only to protein [[translation (genetics)|translation]] but more often it refers to a multi-step process, beginning with [[amino acid synthesis]] and [[transcription (genetics)|transcription]] which are then used for [[translation (biology)|translation]]. Protein biosynthesis, although very similar, differs between [[prokaryote]]s and [[eukaryote]]s. ==Amino acid synthesis== {{main|Amino acid synthesis}} Amino acids are the monomers which are [[polymerized]] to produce proteins. Amino acid synthesis is the set of [[biochemical]] processes ([[metabolic pathways]]) which build the amino acids from carbon sources like [[glucose]]. Not all amino acids may be synthesised by every organism, for example adult humans have to obtain 8 of the 20 amino acids from their diet. ==Transcription== {{main|Transcription (genetics)}} Transcription is the process by which an [[mRNA]] template, encoding the sequence of the protein in the form of a [[genetic code|trinucleotide code]], is transcribed from the [[genome]] to provide a template for translation. Transcription copies the template from one strand of the [[DNA]] double helix, called the [[template strand]]. Transcription can be divided into 3 stages: Initiation, Elongation and Termination, each regulated by a large number of proteins such as [[transcription factor]]s and [[coactivator]]s that ensure the correct gene is transcribed in response to appropriate signals. The DNA strand is read in the 3' to 5' direction and the mRNA is transcribed in the 5' to 3' direction by the [[RNA polymerase]]. ==Translation== {{main|Translation (biology)}} The synthesis of proteins is known as translation. Translation occurs in the [[cytoplasm]] where the [[ribosome]]s are located. Ribosomes are made of a small and large subunit which surrounds the mRNA. In translation, [[mRNA|messenger RNA (mRNA)]] is decoded to produce a specific [[polypeptide]] according to the rules specified by the [[genetic code]]. This uses an mRNA sequence as a template to guide the synthesis of a chain of [[amino acid]]s that form a protein. Translation is necessarily preceded by [[Transcription (genetics)|transcription]]. Translation proceeds in four phases: activation, initiation, elongation and termination (all describing the growth of the amino acid chain, or [[polypeptide]] that is the product of translation). In activation, the correct amino acid (AA) is joined to the correct [[tRNA| transfer RNA (tRNA)]]. While this is not technically a step in translation, it is required for translation to proceed. The AA is joined by its carboxyl group to the 3' OH of the tRNA by an ester bond. When the tRNA has an amino acid linked to it, it is termed "charged". Initiation involves the small subunit of the ribosome binding to 5' end of mRNA with the help of [[initiation factors]] (IF), other proteins that assist the process. Elongation occurs when the next aminoacyl-tRNA (charged tRNA) in line binds to the ribosome along with GTP and an elongation factor. Termination of the polypeptide happens when the A site of the ribosome faces a stop codon (UAA, UAG, or UGA). When this happens, no tRNA can recognize it, but [[release factor|releasing factor]] can recognize nonsense codons and causes the release of the polypeptide chain. The capacity of disabling or inhibiting translation in protein biosynthesis is used by [[antibiotic]]s such as: [[anisomycin]], [[cycloheximide]], [[chloramphenicol]], [[tetracycline]], [[streptomycin]], [[erythromycin]], [[puromycin]] etc. ==Events following protein translation== The events following biosynthesis include [[post-translational modification]] and [[protein folding]]. During and after synthesis, polypeptide chains often fold to assume, so called, native [[secondary structure|secondary]] and [[tertiary structure]]s. This is known as ''[[protein folding]]''. Many proteins undergo ''post-translational modification''. This may include the formation of [[disulfide bridge]]s or attachment of any of a number of biochemical [[functional group]]s, such as [[acetate]], [[phosphate]], various [[lipid]]s and [[carbohydrate]]s. [[Enzyme]]s may also remove one or more amino acids from the leading (amino) end of the polypeptide chain, leaving a protein consisting of two polypeptide chains connected by disulfide bonds. ==See also== *[[Genetic code]] *[[Cistron]] *[[Operon]] *[[lac operon|''lac'' operon]] ==External links== * [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?highlight=translation&rid=cooper.section.1167#1178 Translation of mRNA] Section of ''The Cell: A Molecular Approach'' by Geoffrey M. Cooper * [http://www.scienceaid.co.uk/biology/genetics2/proteinsynthesis.html Science aid:Protein synthesis] For high school * [http://www.accessexcellence.org/AB/GG/protein_synthesis.html Protein Synthesis] * [http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Transcription.html Transcription] *: [http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Translation.html Translation] * [http://learningobjects.wesleyan.edu/proteinsynthesis/ Protein Synthesis Animation] Wesleyan University Learning Objects animation of protein synthesis. * [http://cmol.nbi.dk/models/dynamtrans/dynamtrans.html Interactive Java simulation of transcription initiation.] From [http://cmol.nbi.dk/ Center for Models of Life] at the Niels Bohr Institute. * From RNA to Protein Synthesis [http://www.asterpix.com/console/?avi=7698391 hypervideo]. {{Protein primary structure}} {{protein biosynthesis}} {{Protein topics}} [[Category:Gene expression]] [[Category:Proteins]] [[Category:Chemical synthesis]] [[Category:Metabolism]] [[Category:Protein biosynthesis]] [[ar:تخليق البروتين الحيوي]] [[ca:Síntesi proteica]] [[cs:Proteosyntéza]] [[da:Proteinsyntese]] [[de:Proteinbiosynthese]] [[es:Síntesis proteica]] [[eo:Proteina sintezo]] [[fr:Synthèse des protéines]] [[ko:단백질의 합성]] [[it:Sintesi proteica]] [[ka:ცილის ბიოსინთეზი]] [[hu:Fehérjeszintézis]] [[nl:Eiwitsynthese]] [[ja:タンパク質生合成]] [[no:Proteinsyntese]] [[pl:Biosynteza białka]] [[pt:Síntese protéica]] [[ru:Биосинтез белка]] [[simple:Protein biosynthesis]] [[fi:Proteiinisynteesi]] [[sv:Proteinsyntes]] [[th:การสังเคราะห์โปรตีน]] [[tr:Protein biyosentezi]] [[uk:Біосинтез білків]] [[zh:蛋白質生物合成]]