* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Protein Synthesis
Ribosomally synthesized and post-translationally modified peptides wikipedia , lookup
Protein moonlighting wikipedia , lookup
RNA interference wikipedia , lookup
Western blot wikipedia , lookup
RNA silencing wikipedia , lookup
Molecular evolution wikipedia , lookup
Cell-penetrating peptide wikipedia , lookup
Silencer (genetics) wikipedia , lookup
Deoxyribozyme wikipedia , lookup
Eukaryotic transcription wikipedia , lookup
Peptide synthesis wikipedia , lookup
RNA polymerase II holoenzyme wikipedia , lookup
Protein (nutrient) wikipedia , lookup
List of types of proteins wikipedia , lookup
Metalloprotein wikipedia , lookup
Transcriptional regulation wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Protein adsorption wikipedia , lookup
Point mutation wikipedia , lookup
Polyadenylation wikipedia , lookup
Nucleic acid analogue wikipedia , lookup
Protein structure prediction wikipedia , lookup
Proteolysis wikipedia , lookup
Bottromycin wikipedia , lookup
Gene expression wikipedia , lookup
Amino acid synthesis wikipedia , lookup
Non-coding RNA wikipedia , lookup
Biochemistry wikipedia , lookup
Messenger RNA wikipedia , lookup
Transfer RNA wikipedia , lookup
Expanded genetic code wikipedia , lookup
Epitranscriptome wikipedia , lookup
Protein Synthesis Section 4.4 - 4.5 Molecular Cell Biology Lodish, etc 2000 I. Proteins A. Definition - A linear polymer of amino acids linked together in a specific order or sequence. Formed in the process known as translation. B. Translation 1. A ribosome mediated production of a protein whose amino acid sequence is specified by the mRNA. 2. Translation further requires energy, tRNA and ribosomes made up of proteins and rRNA. C. RNA 1. Three types a. rRNA=ribosomal RNA b. tRNA=transfer RNA c. MRNA=messenger RNA 2. 3. Components a. Bases U Uracil A Adenine G Guanine C Cytosine b. Ribose sugar c. Phosphate ion Base sequence of mRNA determines the primary structure of the protein a. Genetic code - also referred to as the triplet code The set of rules whereby nucleotide triplets in DNA and RNA specify amino acids in proteins 1 - 3 nucleic acids make 1 amino acid/codon - 64 different combinations with the 4 different bases allowed. - make 20 different amino acids - 61 codons specify amino acids - AUG or GUG - start codon - 3 stop or nonsense codons - UAA, UGA, UAG b. D. Reading frame The sequence of nucleotide triplets (codons) beginning with a specific translation start codon (AUG=met) in a mRNA and ending with a stop codon. mRNA 1. Carries the genetic information copied from DNA in the form of a series of three base code words (codons). 2 E. tRNA 1. 2. 3. 4. 5. Transfer RNA is the key to deciphering the code words in mRNA. Carries specific amino acids to the mRNA to synthesize the protein. Can only carry 1 amino acid at any particular time Cell may have many tRNAs for each amino acid. Codons - Anticodons - Codons are the triplet code of bases that designated the amino acid. - Anticodons are the triplet complementary code of the tRNA that the codons attach to. Some tRNAs have unconventional bases that can pair with >1 codon by "wobble pairing" F. II. rRNA 1. Ribosomal RNA associates with a set of proteins to form the complex structure known as a ribosome. 2. Ribosomes are a complex structure made up of two subunits that consist of: Several rRNAs 50+ proteins 3. Subunits a. Each ribosome is made up of two subunits of different densities. b. Prokaryotes - 30S and 50S makes a 70S ribosome. c. Eukaryotes - 40S and 60S makes a 80S ribosome. Protein Formation - Translation A. Review of RNA formation - applies to all three types of RNA 1. Transcription 2. 5' capping 3. 3' poly(A) tail addition 4. splicing 5. transport out of nucleus 3 B. C. Components of Translation 1. mRNA 2. tRNA 3. rRNA - both subunits of the ribosome 4. GTP and ATP 5. amino acids 6. various initiation, elongation and termination factors. Stepwise formation of proteins 1. Initiation – Prokaryotes a. b. c. d. e. 30S ribosome subunit is activated with the addition of GTP and initiation factors. Met attached to tRNA is brought to the 30S subunit. At the same time the mRNA is attached to the ribosome subunit at the start codon position The 50S subunit is combined to the 30S subunit to form the ribosome and the initiation complex. Eukaryotic initiation - substitute 30S for 40S and 50S for 60S. 4 2. Elongation a. 3. The ribosome translocates along the mRNA has two sites - A and P site. A site - amino acid attachment P site - peptide bonding site b. tRNA with amino acids are attached to the A site with the help of elongation factors. If the tRNA and the mRNA match then the amino acid is attached. If they do not, the tRNA is ejected. c. The ribosome translocates along the mRNA and moves the tRNA from the A to P site where a polypeptide bond is formed with the help of an enzyme and 3 ATP. Termination 5 a. b. D. Ribosome translocates to a stop codon. Release factors attach to the A site of the Ribosome - release factors have a similar shape of a tRNA - There are 3 different release factors (RF1, RF2, and RF3), and each one attaches for a different stop codon. c. Release factors separate the ribosome into its subunits and thus stops elongation and protein synthesis. Regulation of Protein Synthesis 1. 1 typical eukaryotic protein takes 30-60 seconds to be synthesized. 2. There are 2 factors that effect synthesis a. Multiple ribosomes working together. b. Rapid recycling of ribosome after termination 6