Protein synthesis and processing Flashcards
nucleolus
where ribosomes are assembled
tRNA
possess unique 3 anti-codons, (cloverleaf structures)
three steps to charge a tRNA
- activation of amino acid
- addition of amino acid to tRNA
- proper folding of tRNA ( brings amino acid to ribosome)
difference of mRNA in prokaryotes and eukaryotes
monocistronic ( eukar) - one gene codes for one protein
polycistronic ( pro) - one gene codes for more than one protein
20 different aminoacyl tRNA synthetase
- recognizes the correct amino acid
- the correct codon on the mRNA
Shine-Dalgarmo sequence
mRNA sequence that binds to complementary base pairs in 16S rRNA in prokaryotes
Small Ribosomal subunit
binds to 5’ m7G cap of the mRNA then slides along mRNA until it finds the start codon
Monocistronic dis. and adv.
slower but less prone to accident, less expensive
Polycistronic dis. and adv.
faster, more prone to accident, more expensive, more waste
Three adjacent tRNA binding sites on ribosome
A (aminoacyl) site : Arrival
P (peptidyl) site: Pause
E (exit) site: Exit
A site
where tRNA arrives
P site
where polypeptide chain is main and waits for right amino acid to be brought by tRNA
E site
where tRNA is punted off the complex and hopefully recycled and charged again.
Decoding centre
within small 40s ribosomal subunit that ensures proper aminoacyl tRNA pairs with codon
Steps in specificity of amino acid incorporation during translation
- correct amino acid /tRNA (ensured by PABP)
- simple base pairing
- Decoding centre
Release factor
- causes structure to come apart
- causes ribosomal subunits and polypeptide to be released
Post translational modification
chemical mod of a polypeptide chain after translation
Types of post trans mods
Glycolsyation
Lipid addition
Phosphorylation
Phosphorylation
Phosphate addition on serine/threonine or tyrosines or tyrosines by specific protein kinases to form phosphoproteins.
Glycosylation
carbohydrate addition to form glycoproteins
Lipid addition
lipid addition to lipoproteins
