* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download The genetic code
Ribosomally synthesized and post-translationally modified peptides wikipedia , lookup
Biochemical cascade wikipedia , lookup
Western blot wikipedia , lookup
Evolution of metal ions in biological systems wikipedia , lookup
Protein–protein interaction wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Eukaryotic transcription wikipedia , lookup
Peptide synthesis wikipedia , lookup
Silencer (genetics) wikipedia , lookup
RNA polymerase II holoenzyme wikipedia , lookup
Paracrine signalling wikipedia , lookup
Protein structure prediction wikipedia , lookup
Point mutation wikipedia , lookup
Metalloprotein wikipedia , lookup
Polyadenylation wikipedia , lookup
Two-hybrid screening wikipedia , lookup
Amino acid synthesis wikipedia , lookup
Transcriptional regulation wikipedia , lookup
Biochemistry wikipedia , lookup
Gene expression wikipedia , lookup
Proteolysis wikipedia , lookup
Transfer RNA wikipedia , lookup
Biosynthesis wikipedia , lookup
Messenger RNA wikipedia , lookup
Epitranscriptome wikipedia , lookup
Gene expression Translation Genetic code The genetic code is a set of rules defining how the four-letter code of DNA (RNA) is translated into the 20-letter code of amino acids, which are the building blocks of proteins. The characteristics of the genetic code Triplet code Degenerate (redundant) Unambiguous Nonoverlapping Comma less Universal Genetic code table Translation Translation is the synthesis of proteins directed by a mRNA template. Principle: Conditions: a template is required mRNA Ribosomes Amino acids tRNAs Enzymes, translation factors Energy (ATP, GTP) Aminoacyl-tRNA synthesis a ribosome Initiation of translation (prokaryotic cells) 1. 2. 3. 4. 5. 6. 7. 8. fmet-tRNA formation 30 S + IF3 → dissociation of the ribosome + mRNA fmet-tRNA is brought to start codon AUG (IF2/GTP → IF2/GDP) fmet-tRNA recognizes AUG: the anticodon UAC (fmetтРНК) base-pairs with a complementary codon AUG on mRNA +IF1 which binds A site and blocks it + 50 S → 70 S (reassociation of the ribosome) Dissociation of initiation factors (IF1,2,3) fmet-tRNA is at Р site of the ribosome, А site is empty The selection of an initiation site (AUG codon) depends on the interaction between the 30S subunit and the mRNA template. Shine-Dalgarno (SD) sequence (AGGAGG) is a ribosomal binding site in prokaryotic mRNA, generally located around 8 bases upstream of the start codon AUG. SD is complementary to a pyrimidine-rich sequence at 3’end of 16 S rRNA in a small subunit. Elongation of translation (prokaryotic cells) 1. Formation of the next aminoacyl-tRNA 2. The aminoacyl-tRNA is brought into A site of the ribosome (Tu/GTP → Tu/GDP) 3. Codon recognition: the mRNA codon in the A site of the ribosome forms hydrogen bonds with the anticodon of an entering tRNA 4. Peptide bond formation: an rRNA molecule catalyzes the formation of a peptide bond between the amino acid in the P site with the new amino acid in the A site. (23 S rRNA in the 50S ribosomal subunit has peptidyl transferase activity) 5. Translocation of the ribosome by one codon (G/GTP → G/GDP) 6. Regeneration of Tu/GTP: Tu/GDP + Ts → Tu/Ts + GDP Tu/Ts + GTP → Tu/GTP + Ts Termination of translation (prokaryotic cells) Stop codons: UAA, UAG, UGA Release factors: RF1, RF2, RF3, RRF RF1 recognizes UAG and UAA RF2 recognizes UGA and UAA These factors trigger the hydrolysis of the bond in peptidyl-tRNA and the release of the newly synthesized protein from the ribosome. RF3 facilitates binding of RF-1 or RF-2 to the ribosome and their release. It has GTPase activity. RRF (ribosomal recycling factor) is required for release of uncharged tRNA from the P site, and dissociation of the ribosome from mRNA with separation of the two ribosomal subunits. a polysome Several ribosomes can translate an mRNA at the same time, forming a polysome (a polyribosome). Translation properties in prokaryotic cells Ribosomes 70S (30S, 50S) In eukaryotic cells 80S (40S, 60S) The first amino acid formylmethionine (fmet) methionine (met) Initiation factors IF1, 2, 3 eIF 1, 2, 3, 4A, 4B, 4C, 4Е, 5 etc. (12) Selection of the start codon Shine-Dalgarno sequence Cap (the scanning hypothesis); Kozak sequence; an internal ribosome entry site in the 5'UTR Assembly of initiation complex 30S + mRNA + fmet-tRNA or 30S + fmet-tRNA + mRNA 40S + met-tRNA + mRNA Translation properties in prokaryotic cells in eukaryotic cells Elongation factors EF1 (Tu), EF2 (Ts), EF3 (G) eEF1, eEF2 Release factors RF1, RF2, RF3, RRF eRF1, eRF3 Location in the cell Cytoplasm Cytoplasm, ER, mitochondria Transcription and translation are coupled Transcription and translation are spatially and temporally separated. Transcription occurs in the nucleus to produce a pre-mRNA molecule. The pre-mRNA is typically processed to produce the mature mRNA, which exits the nucleus and is translated in the cytoplasm. Processing of proteins Processing of proteins is a complex of post-translational modifications of the protein molecules (protein maturation) Steps of processing Proteolytic cleavage (removing segments of the polypeptide chain by enzymes called proteases) Chemical modification (Individual amino acids in polypeptidemight be modified by attachment of new chemical groups) Folding (a process in which a polypeptide folds into a specific, stable, functional, three-dimensional structure; formation of tertiary structure of the protein) by foldases and chaperones Association of protein subunits