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Ingredients needed for transcription in bacteria
- DNA template: to serve as a blueprint for the RNA sequence
- Ribonucleotides: to serve as a monomers for RNA polymerization
- RNA Polymerase: catalyses synthesis of RNA
Naming of parts
- Promoter: extremely important for the recognition of the RNA
- +1 site: site is sort of what is called the start of the transcription
- Coding sequence: region of gene that codes for the protein
sense strand vs anti-sense strand
sense strand is the nontemplate strand, the anti-sense strand is the template strand
Initiation of transcription in prokaryotes
1. Polymerase binds to promoter sequence in duplex DNA. "closed complex"
2. Polymerase melts duplex DNA near transcription start sit, forming a transcription bubble. "Open complex"
3.Polymerase catalyzes phosphodiester linkage of two initial rNTPs
Elongation in Prokaryotes
Polymerase advances 3'to5' down template strand, melting duplex DNA and adding rNTPs to growing RNA
During transcription we transiantly produce a funky hybrid of DNA and RNA
Formation of phosphodiester bond
Polymerization involves the formation of a phosphodiester linkage between the free 3' hydroxyl of the growing RNA chain and the alpha phosphate group of the incoming rNTP
At transcription stop site, polymerase releases completed RNA and dissociates from DNA
Holoenzyme scans along the DNA until it encounters a promoter region to bind to and form a closed complex.
Consist of core enzyme and sigma actor.
Task of sigma factor
- Found in the Holoenzyme
- Its task is to find the promoter
- "find where the gene is"
Alpha subunit and Beta subunit are important in terms of....
They are important in terms of catalysis
Omega does what?
Is there for stabilizing
Why is B' (beta prime) important
Important to grab DNA onto the template
How does the Sigma (σ) factorrecognize the promoter region?
by binding to specific sequence motifs, whic
h areessential for promoter activity (the -10 and -35 regions)
Process in which messanger RNA is translated into proteins
Three roles of RNA
mRNA: Genetic information DNA in form of codons
tRNA: key to decipher the codons in mRNA. Each tRNA has an associated amino acid and anticodon
rRNA: associates with proteins to form ribosomes
What is never translated?
tRNA and rRNA, there functional identity is to transcript
Prokaryotes subunits are made of what?
rRNA and proteins
Initiation of Prokaryotic translation
- Initiation Factors (IFs) associate with the 30S subunit forming the preinitiation complex
- IF1 and IF3 assists the loading of mRNA and the initiation aminoacyl-tRNAforming the 30S initiation complex which binds the transcript at the initiationcodon, AUG
- IF1 and IF2-GTP facilitate theloading of the 50S subunit forming the 70S initiation complex
Elongation in Prokaryotic translation
- Elongation Factors (EFs) arerequired for the stepwise additionof amino acids
- It’s a ribozyme - the 23S rRNA -that carries out thepeptidyltransferase reaction
Termination in Prokaryotic translation
- When the mRNA ribosome-tRNA-peptidyl complex reaches a stopcodon, Release Factors(RFs) mediate thetermination of proteinsynthesis.
- RF1 and 2 mimic tRNA
- RF3-GTP catalyzes the cleavage of the peptidyl tRNA releasing the protein chain
When can you start translation
Not until those tRNA molecules are coupled with their bonded amino acids forming an Amimoacyl-tRNA
Wobble base pair in the first, or wobble position of anticodon
Wobble base pairs in third or wobble, position of codon of an mRNA