1.
Contact me at kgahern@davincipress.com /
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Facebook (kevin.g.ahern)
2.
Download my free biochemistry book at
http://biochem.science.oregonstate.edu/biochemistry-free-and-easy
3. Take my free iTunes U course at https://itunes.apple.com/us/course/biochemistry/id556410409
4.
Check out my free book for pre-meds at http://biochem.science.oregonstate.edu/biochemistry-free-and-easy
5. Lecturio videos for medical students - https://www.lecturio.com/medical-courses/biochemistry.course
6.
Course video channel at http://www.youtube.com/user/oharow/videos?view=1
7. Check out all of my free workshops at http://oregonstate.edu/dept/biochem/ahern/
123.html
8. Check out my
Metabolic Melodies at http://www.davincipress.com/
9. My courses can be taken for credit (wherever you live) via
OSU's ecampus. For details, see http://ecampus.oregonstate.edu/soc/ecatalog/ecourselist
.htm?termcode=all&subject;=
BB
10. Course materials at http://oregonstate.edu/instruct/bb451
1. The
TATA box is not found in front of all eukaryotic genes, but is essential for strong transcription.
2.
RNA Polymerase II in eukaryotes differs from
RNA polymerase in
E. coli in not binding to the
DNA directly, but must bind to transcription factors at the promoter. For genes with a TATA box, the transcription factor
TFIID binds first. It contains a subunit called
TBP (TATA-Binding
Protein) that recognizes and binds to the TATA sequence
Highlights Translation I
1. Prokaryotic ribosomes are a 70S multi-protein, multi-RNA complex, consisting of a large 50S subunit and a smaller 30S subunit.
2. Translation is performed by ribosomes on mRNA and occurs in
the 5' to 3' direction at about the same as the rate of transcription (45-50 bases or 15-17 amino acids per second).
3. As polypeptides are being synthesized, the previously synthesized chain is attached to the free amine of the incoming (new) amino acid and the entire complex is attached to the 'new' tRNA.
4. Transcription and translation are coupled together in bacteria, but not in eukaryotes.
5. Translational accuracy is about one
error per thousand to ten thousand amino acids.
Greater accuracy would slow translation down.
6. tRNAs have extensive self-complementary regions. They are typically 73-93 bases long, with duplex regions at least partly in the A form. The shape of tRNAs is that of an 'L'. At the 3' end is a
CCA.
7. Enzymes that catalyze the linkage of amino acids to tRNA's 3' or 2' ends are called aminoacyl-tRNA-synthetases (we nicknamed them "
Terry" in class). There are 20 of these enzymes - one for each amino acid.
8.
Amino acids are linked to tRNAs by ester bonds between the carboxyl group of the amino acid and either the 2' or 3' hydroxyl of the ribose of the terminal adenosine residue of the tRNA. The ester bonds are extremely unstable in water and must be protected from it.
9. The anticodon loop has three bases complementary to the codon in the mRNA. tRNAs provide the translation
function between nucleic acid sequence and amino acids. The anticodon loop frequently contains the inosine base. The base at the 3' end of the codon of the mRNA (corresponds to the base at the 5' end of the anticodon in the tRNA) is called the wobble base because it is less important for specifying the amino acid.
10.
Aminoacyl-tRNA synthetases have the ability to recognize and correct errors in joining of amino acids to tRNAs. If one puts the wrong amino acid on the end of a tRNA and then adds an appropriate aminoacyl-tRNA synthetase, the amino acid is readily removed.
11. Two regions of aminoacyl-tRNA synthetases are important for editing - called the activation site and the editing site.
12. Amino acyl tRNA synthetases differ in the way they bind tRNAs and in which hydroxyl of the ribose ring they attach the amino acid to.
Class I enzymes attach the amino acid to the hydroxyl on carbon #2. Class II enzymes attach the amino acid to the hydroxyl on carbon #3.
13.
Base pairings in
RNA are slightly different than in DNA. G-U base pairs are not unstable. In addition, inosine can pair with
C,U, or
A.
14. In the genetic code, there are 64 possible combinations of the bases of the codon. Three of them (
UAA,
UGA, and
UAG) are used as 'stop' codons. They tell the ribosomes where to stop making protein. A start codon is (
AUG).
15. Ribosomes have three sites for binding/holding/releasing tRNAs. They are called the
A,P, and E sites, corresonding to the order in which tRNAs move through them.
16. The
Shine-Dalgarno sequence (GGAGG) is located near the AUG start codon in prokaryotic sequences. It is complementary to a sequence in the 16S rRNA and serves to help align the ribosome with the start site for translation in prokaryotes.
17. In prokaryotes, the first amino acid incorporated into a protein is a formylated form of methionine called fMet. Formylation of methionine in prokaryotes protects the otherwise free amino end from reacting intramolecularly and terminating transcription.
- published: 04 Mar 2014
- views: 3958