Daily Newsletter January 24, 2012
Today's Topic:Bacterial Translation
As with other genetic processes, translation in bacteria is similar to what occurs in eukaryotes. The ribosome functions in a similar way, but the bacterial ribsome is smaller (70s, instead of 80s). The sizes of the rRNA are different. Some molecular processes are different, but when viewed from a larger perspective, you still have initiation, elongation and termination. The same genetic code is used, the ribosome reads triplet nucleotides (codons), tRNAs carry amino acids, and ribosomes catalyze peptide bond formation.
Some points to remember:
I am confident that each student can describe the basic mechanisms of translation, and with the notes above, compare translation in bacteria and eukaryotes. So today, students should focus on secretory systems in bacteria.
NOTE: If you are not confident in your ability to describe translation, write up a quick description in your blog.
Daily Challenge: Bacterial Secretion Systems
In your blog today, write about the different ways bacteria can get proteins either into the cellular membrane or exude them out of the cell to the extracellular fluids. Specifically concentrate on these topics: general secretory system, signal recognition protein, sec B, and the Type I Secretory System. I also want you to read about the type III secretory system and write a paragraph about it.
As with other genetic processes, translation in bacteria is similar to what occurs in eukaryotes. The ribosome functions in a similar way, but the bacterial ribsome is smaller (70s, instead of 80s). The sizes of the rRNA are different. Some molecular processes are different, but when viewed from a larger perspective, you still have initiation, elongation and termination. The same genetic code is used, the ribosome reads triplet nucleotides (codons), tRNAs carry amino acids, and ribosomes catalyze peptide bond formation.
Some points to remember:
- Bacteria use f-MET (N-formyl methionine) instead of just MET.
- Initation in bacteria requires three initiation factors that bring the ribosomal sub-units together on an mRNA molecule.
- Peptidyltransferase activity of the ribosome is carried out by ribosomal RNA, not protein.
- Translation terminates upon reaching a stop codon, which causes the ribosome to pause because it cannot find an appropriate tRNA; a release factor enters the A site and triggers peptidyltransferase activity.
- Ribosome release factor and EF-G bind to the A site to dissociate the two ribosomal subunits from the mRNA.
- Transcription and translation in prokaryotes are coupled (Polyribosome).
- RNA polymerase pauses during transcription to allow the slower translating ribosomes to stay close. This minimizes exposure of mRNA to degradative cellular enzymes.
- tmRNA rescues ribosomes stuck on damaged mRNA that lacks a stop codon.
- After translation, the N-terminal amino acid (N-formylmethionine) can be removed by methionine deformylase.
- An inactive precursor protein can be cleaved into a smaller active protein, or other groups can be added to the protein (for example, phosphate or AMP).
- Chaperone proteins help translated proteins fold properly.
I am confident that each student can describe the basic mechanisms of translation, and with the notes above, compare translation in bacteria and eukaryotes. So today, students should focus on secretory systems in bacteria.
NOTE: If you are not confident in your ability to describe translation, write up a quick description in your blog.
Daily Challenge: Bacterial Secretion Systems
In your blog today, write about the different ways bacteria can get proteins either into the cellular membrane or exude them out of the cell to the extracellular fluids. Specifically concentrate on these topics: general secretory system, signal recognition protein, sec B, and the Type I Secretory System. I also want you to read about the type III secretory system and write a paragraph about it.
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