Lecture 10 Flashcards
What does transcription do?
makes an RNA copy of DNA
What RNA transcribes most rRNA genes?
RNA polymerase 1
What RNA polymerase transcribes all protein-coding genes, miRNA genes, plus genes for other noncoding RNA’s?
RNA polymerase 11
What RNA polymerase codes tRNA genes, 5s rRNA genes and genes for many other small RNA’s?
RNA polymerase 111
What form of rna carries amino acids for translation?
tRNA
What rna codes for proteins?
mRNA
What rna is involved in gene expression?
micro RNA
What rna form the core of the ribosome’s structure and catalyze protein synthesis
Ribosomal RNA
Can RNA act as an enzyme (ribozyme), catalyzing chemical reactions?
yes
What initiates transcription to happen?
promoter
What is the TATA box?
is contained in the promoter and recruits general transcription factors
What is the role of the general transcription factors?
Seperate the double stranded DNA, allowing RNA polymerase II access to the template strand
What is it called when removing an intron?
splicing
What is the region called that has been spliced
splicesome
What does it mean when the mRNA is capped, polyadenylated, and spliced?
Ready for export out of the nucleus
What happens during translation?
Translation decodes the mRNA and producing the corresponding protein
What does translation require?
mRNA
Ribosome
aminoacytl-tRNA
What is the largest and abundant protein complexes in cells?
Ribosome
What type of RNA does ribosomes have?
rRNA
What links the proper amino acid to the corresponding tRNA?
tRNA synthase
What enzyme is highly specific?
tRNA synthase
what happens at the A site?
first binding site for aminoacyl-tRNA
What happens in the P site?
tRNA linked to the polypeptide
What happens at the E site?
Exit site for the tRNA
What is the mRNA ribosome complex called?
polysomes
What does polysome analysis indicate?
Translation activity of cells
What end of the protein starts folding as soon as it emerges from the ribosome?
N -terminal
Cotranslational folding of proteins only occurs to what type of proteins?
less complex proteins
What is the role of a molecular chaperone?
Help with protein folding
What do chaperones require?
ATP
What is the endoplasmic reticulum functions?
- protein translocation
- protein folding
- protein glycoslytion
- protein quality control
- calcium iron storage
What is the structure of the ER?
Membrane network, distributed by microtubule interactions
What materials are translated at the ER?
Transmembrane proteins and soluble lumenal proteins
What ensures proper insertion into the membrane or delivery into the lumen of the ER?
Ribosome linkage with protein translocator
What is the n terminus?
lumenal
What is the C - terminus?
cytosol
Where are the n and c termini located?
cytoplasm
What happens during N-linked glycosylation?
Modification of an amino group
What happens in o-linked glycosylation?
Modification of OH group
Most proteins that are translated and translocated at the ER become what?
glycosylated (both soluble and transmembrane proteins)
What does glycosylation increase?
Increase stability of secreted proteins
Why is the glycosylation of surface proteins important?
Important for recognition of self vs foreign (immune system)
Where do newly synthesized proteins fold?
In the ER
What is allowed to leave the ER?
Only folded proteins - unfolded proteins remain in the ER with chaperones
What happens to proteins that are not properly fold in to the ER?
They are retro translocated to the cytoplasm, ubiquitinated and degraded by the proteasome
What is retrotranslocation mediated by?
By the same translocator protein that allows for protein import into the ER
