Download Bacterial Disease Lecture 1: Transcription, Translation, and Regulation in Bacteria - Prof and more Study notes Biology in PDF only on Docsity! January 17, 2013 Bacterial Disease Lecture 1 1) Transcription/Translation Review in Bacteria 2) Transcription diagram 3) Only 1 RNA polymerase will track along DNA without sigma; cannot find promoters on its own 4) Eventually sigma and RNA poly will bind at a promoter site and form a closed promoter complex at the promote -means ready to start transcription 5) Consensus E. Coli promoter- is TTGACA; the center of it is the -35; then 17-19 bases; then TATAAT (consensus) at -10; then more spaces to the +1. The +1 is where it is ready to start. 6) The closer a promoter sequence is with the consensus, the stronger the interaction with the promoters, etc. 7) DNA unwinds.. 8) Diagram 2 9) 1.initiation a) Sigma leaves and the rest continues transcription 10) 2. Elongation a) Growing mRNA 11) 3. Termination a) Termination sequences that will signal termination and transcription b) Different kinds of termination sequences 12)Factor-independent – GC-rich hairpin followed by a string of US (in mRNA) 13) Factor dependent 1. -No consensus sequence 2. -Involves Rho factor; Rho binds to factor-dependent sequence… 14)Translation Overview. Remember tRNA links the info to the mRNA 1. Translation in Bacteria a. Open reading frame; ribosomal subunit- 30s and 50s; b. Composed of individual proteins that make up the full ribosome c. Can be relative to antibiotic resistance in pathogens d. Initiation of translation - the first codon in the open reading frame is usually AUG, the open loop will read from 5’ to 3’ as CAU (but looks like this UAC from 3’ to 5’)- antiparallel base pairing e. Opposite end of tRNA is a modified form of methionine- first amino acid typically 2. Lets say they already added 4 amino acids to the polypeptide chain… attached to the tRNA that is now in the P site; we are getting ready to add the next amino acid to the A site a. This is part of elongation 3. Base pairing between the TRNA and the next triplet; very energy expensive process 4. To link the next amino acid, a peptide bond must form 5. Peptide Bond formation is catalyzed by 23s rRNA (ribosomal RNA). 6. As soon as peptides from P site attached to A site, and grow, and reattach to the P site, while the A site leaves to get ready for more to be reaccepted and grow the chain Termination 1. Stop codons 2. UGA, UAA, UAG all stop codons 3. The release factors of the stop codons will cause them to dissociate and stop the process. Transcription energy expenditure- high also - Energy in form of ATP or GTP; cells want to tightly regulate their energy currency - Once a protein encoding gene is transcribed, and then it will be translated….etc.. And it doesn’t really need it, it can waste a ton of energy and damage or kill the cell - Most of the time there will be a lot of regulation of transcription and translation for when the specific protein is actually needed Transcriptional regulation 1. Negative control - keeping it from happening; using a repressor which binds within promoter or downstream from promoter…when it binds downstream, it acts as a road block- when it binds at the promoter, it will block it 2. Positive control - an activator is used here in order to enhance RNA polymerase reaction with promoters; the closer the promoter to the consensus, the better and stronger they are 3. The sigma factor may not be able to recognize a less consensus sequence, so in order for them to recognize it, you need an activator 4. Activator will bind at an activator site and it will bind so it doesn’t impede on RNA poly from binding in the TCCAAC.. And will help stabilize RNA pol binding 5. Without the activator, RNA poly cannot bind as tightly and cannot be as efficient
