CSF: genes to proteins Flashcards
transcription 3 steps
initiation, elongation and termination
initiation
polymerase binds to promoter
elongation
moves downstream through the gene transcribing RNA
termination
detaches after terminator reached
template strand
3’ to 5’
non-template strand
5’ to 3’
what does the TATA box do
it is the promoter or start of the transcription
transcription factors
bind to DNA
what forms a transcription initiation complex
RNA polymerase II and transcription factors
how many nucleotides can RNA polymerase open at a time?
10-20
which is stronger hydrogen or phosphodiester bonds?
phosphodiester bonds are stronger
elongation (2 points)
- complementary RNA nucleotides are added to 3’ end of growth transcript
- double helix reforms
termination
- after transciprtion of polyadenylation signal nuclear enzymes release pre-mRNA and RNA then dissociates from DNA
there is less what in RNA synthesis than DNA?
less fidelity
capping
modified guanine nucleotide added to the 5’ end
tailing
50-250 adenine nucleotides are added to the 3’ end
capping and tailing are thought to
facilitate export, confer stability, facilitate ribosome bonding in cytoplasm
splicing
introns removed from the transcript
exons
coding regions (including UTRs)
introns
non-coding regions intervening exons
UTR
untranslated regions at 5’ and 3’ ends
splicosome
Large complex of proteins and small RNAs
Alternative splicing allows for
multiple gene products from the same gene
protein sequence determines
final function
structure
determines function
what do DNA mutations affect
ability of protein function
what does RNA change about nucleotides
thymine becomes uracil T to U
what happens to mature mRNA transcript (ribosome translation)
exits nucleus and is bound by a ribosome
tRNA carrys
anticodons
what forms between anti codons and codons
hydrogen bonds
4 important ribosomal sites:
mRNA binding site
A site
P site
E site
A site
holds ‘next in line’ tRNA
P site
holds tRNA carrying growing peptide
E site
`tRNA exit from here
mRNA binding site
where RNA binds - on the smaller subunit
tRNA is
the physical link between the mRNA and amino acid sequence of proteins
initiation; what is initiator tRNA
a tRNA carrying a methionine (a starting amino acid)
Translation initiation 1/4
- small ribosomal subunit with bound initiator tRNA binds 5’ cap of mRNA
Translation initiation 2/4
- small ribosomal subunit scans downstream to find translation start site AUG
Translation initiation 3/4
- hydrogen bonds between initiator anticodons and mRNA
Translation initiation 4/4
- Large ribosomal subunit binds completing initiation complex
what is required for initiation translation
GTP energy - guanosine triphosphate
codon recognition
base pairs with the complementary anticodon GTP invested to increase accuracy/efficiency
Translocation
move tRNA from A to P site, tRNA in P site moves to E and is released. Energy is required
where and how are empty tRNAs filled
in the cytoplasm aminoacyl-tRNA synthase
termination translation 1/3
- ribosome reaches stop codon on mRNA (site A release factor)
termination translation 2/3
- Release Factor promotes hydrolysis, last amino hydrolyzed releasing polypeptides
termination translation 3/3
ribosomal subunits and other components dissociate requiring hydrolysis of two GTP molecules. Ribosome can be re-used
primary protein bonds
covalent bonds between amino acids - relatively strong
primary protein secondary structures
secondary structures start to form as soon as it leaves the ribosome
primary is determined by
DNA sequence
secondary bonds
weak hydrogen bonds
secondary forms
beta sheets and alpha helix
tertiary shape
3D stabilized by side chain interactions
tertiary TP name
transthyretin polypeptide
quaternary structure
transthyretin protein
quaternary structure
multiple proteins associated forming a functional protein
do all proteins for quaternary structures?
not all do
signal peptide
at N terminus of protein
SRP
signal recognition particle
signal peptides direct ribosomes to rough ER 1
- polypeptide synthesis begins
signal peptides direct ribosomes to rough ER 2
- SRP binds to signal peptide
signal peptides direct ribosomes to rough ER 3
- SRP binds to receptor protein
signal peptides direct ribosomes to rough ER 4
- SRP detaches and polypeptide synthesis resumes
signal peptides direct ribosomes to rough ER 5
- signal-cleaving enzyme cuts off signal peptide
signal peptides direct ribosomes to rough ER 6
- completed polypeptide folds into final conformation, a secetroy protein is solubilized in lumen, membrane protein remains anchored to the membrane
post transitional modifications
addition of groups to a protein
addition of phosphate
phosphorylation
addition of methyl
methylation
addition of acetyl
acetylation
addition of Biotin
biotinylation
addition of carboxylic acid
carboxylation
what can confer activity
phosphorylation and enzyme cleavage
ability to interact with other molecules
biotinylation, methylation of histones
direct to a particular location
ubiquination
mutations
can affect the structure and function of a protein
large scale
chromosomal rearrangment
small scale alterations
one or a few neucleotides altered
point mutations substitutions, are they major or minor
one base replaced by another; minimal to major effect
point mutations insertion or deletions, are they major or minor
can cause frame shift; major
silent mutations
the mutation occurs however does not affect the outcome of the protein wanting to be made
frameshift caused by
insertion or deletion
what prime end is more catastrophic
more towards the 5’ end is more catastrophic
