Lecture 3: Gene Expression: Translation / Protein Synthesis Flashcards
Transcription + Translation =
Gene Expression
Section of DNA (a gene) being transcribed & translated to produce a protein.
gene expression
Genes can be turned on and off (called ___________) by various mechanisms.
Occur at any point during gene expression, but most commonly occurs at the
level of ___________.
gene regulation
transcription
Gene regulation:
Signals from the environment or from other cells activate proteins called
_____________ factors which control the level of transcription.
transcription
What are regulatory elements in transcription process?
Enhancers and suppressors
-Genes are turned on and off in different patterns during development stages
There are the 20 biologically active amino acids in humans. They are
encoded directly by the codons of the universal genetic code are called
__________ or ____________ amino acids.
standard, canonical
There are _____ Essential amino acids (indispensable) amino acid , which
cannot be synthesized de novo ), and have to get them from diet.
9
– histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine,
tryptophan, and valine.
Basic amino acid structure:
a central alpha carbon covalently bonded to…
-a carboxyl group
-an amine group
-a hydrogen
-a variable R group
a sequence of three nucleotides that together form a unit of genetic code in a DNA or RNA molecule, and the genetic information is translated into proteins by living cells.
Codon
Amino acids are the structural units (monomers) that make up
proteins.
There are the 20 biologically active amino acids in
Humans
They are
encoded directly by the codons of the universal genetic code are called
standard or canonical amino acids
There are _________ Essential amino acids (indispensable) amino acid , which
cannot be synthesized de novo ), and have to get them from __________
There are nine Essential amino acids (indispensable) amino acid , which
cannot be synthesized de novo ), and have to get them from diet
nine essential AA
histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine,
tryptophan, and valine
Amino Acids join together to form short polymer chains called _____________
or longer chains called either __________ or __________.
*
peptides
or longer chains called either polypeptides or proteins.
*
Basic Amino Acid Structure
a central alpha carbon covalently linked to:
a central alpha carbon covalently linked to:
- Carboxyl group
- an amine group
- a hydrogen
- a variable R group
The Genetic Code
Codon
– a sequence of three nucleotides that together form a unit of genetic code in a DNA
or RNA molecule, and the genetic information is translated into proteins by living
cells.
The Genetic Code
Nonoverlapping and universal in
plant and animal kingdoms (ex. Mitochondrial code)
The Genetic Code
Degenerate (wobble base codon
– The first two positions of the mRNA codon observe Watson-Crick base pairing rules
(A-U, C-G) The third position exhibits wobble
The genetic code
codon read by
Read by complementary tRNA linked to aa
Initiation codon
AUG (met)
Stop codons
UAA, UGA, UAG
Translation
Information what
high what
- Information decoding
- High energy consuming process
– consumes 90% of cells energy
– 4 ATP / aa
Protein Synthesis Players
- Ribosome / rough ER / rER (rRNA + protein)
- tRNA = anticodon with aa
- mRNA = codon
Protein Synthesis Players
Ribosome has 2 sites which associate with mRNA
– P site (initaition)
– A site (elongation)
Protein Synthesis Steps
Initiation
– 1st aa always methionine (Met) at P site
– Template = mRNA
– mRNA moves down in register (A site) and codon is read by
anticodon of tRNA
Protein Synthesis Steps
Elongation
– new aa brought in to match new codons and peptide bonds formed
Protein Synthesis Steps
Termination
Stop codon (UGA,UAA,UAG)
Massager RNA (mRNA)
Carries instructions from DNA to where
tells the ribosome what
- Carries instructions from DNA to the rest of the ribosome.
- Tells the ribosome what kind of protein to make
Transfer RNA (tRNA)
A go-getter.
Gets the right
parts to make the
right protein
according to
mRNA instructions
Ribosomal RNA (rRNA)
Part of the _____
helps in ______
- Part of the structure of a ribosome
- Helps in protein production
Ribosomal RNA (rRNA)
Ribosomes contain two ______ and 50 or more ________
rRNA sequences are widely used for ________
- Ribosomes contain two major rRNAs and 50 or more
proteins - rRNA sequences are widely used for working out
evolutionary relationships among organisms
Ribosomal RNA (rRNA)
Prokaryotic rRNA
size 70s
large subunits- 50s and 23s
small subunits: 30s
Ribosomal RNA (rRNA)
eukaryotic rRNA size
size: 80s
large subunits- 60s and 28s
small subunit- 40s
End Product of protein synthesis
- The end products of protein synthesis is a primary structure of a
protein. - A sequence of amino acid bonded together by peptide bonds.
Post Translational Modification and Regulation
Recognition of
Signal Peptide
Post Translational Modification and Regulation
Glycosylation
O linked
N linked
addition of sugars to proteins destined to be membrane or
secreted
– “O” linked- serine/threonine in golgi
– “N” linked - asparagine in ER
Post Translational Modification and Regulation
Proteolysis cleavage-
Truncation
Post Translational Modification and Regulation
_______ bonds bridges
Attachment or binding of groups _________
Disulfide bonds bridge
NAD,Zn,Mg,FAD
Post Translational Modification and Regulation
Assembly of ______
multiple subunits
Post Translational Modification and Regulation
______ group modifications
R
R -Group Modifications
- Phosphorylation (via kinase on -OH group of
serine/threonine/ tyrosine) - Methylation
- Acetylation (palmitylation C16 via thioester with
cysteine, myristication C14 at amino-terminal
glycine) - Isoprenation (farnesyl,guanosyl groups)
- Hydroxylation
Phosphorylation via
kinase on -OH group of
serine/threonine/ tyrosine)
Acetylation
palmitylation C16 via thioester with
cysteine, myristication C14 at amino-terminal
glycine)
Isoprenation
arnesyl,guanosyl groups
Maturation of Human Pre-Pro-insulin
Pre-pro-protein
A protein precursor that contains a ______________
a protein precursor that contains a signal peptide
sequence; it is a nonpolar sequence at the head of the
growing polypeptide chain and contains many
hydrophobic amino acids residues.
Maturation of Human Pre-Pro-insulin
Pre-pro-protein
required for its transfer into the ________ of the
______________; the signal sequence is then
cleaved to form the protein or proprotein.
required for its transfer into the cistern of the
endoplasmic reticulum; the signal sequence is then
cleaved to form the protein or proprotein.
Insulin Protein Precursors: Pro-Insulin
Pre-pro-sequence
About ___ non polar aa guide the protien to be
– About 30 non-polar aa guide the
protein to be secreted out of cells or
into different compartment of the cell
sub-organells
Insulin Protein Precursors: Pro-Insulin
Pro-sequences
Areas where
Usually in the transition of
May be involved In
– areas in the protein that are essential
for its correct folding
– usually in the transition of a protein
from an inactive to an active state.
– Pro-sequences may also be involved in
pro-protein transport and secretion
Clinical Usage of C peptide Measurement
- Patients with ________ may have their C-peptide levels measured as a means of
distinguishing type ________ from type _________ or __________
- Patients with diabetes may have their C-peptide levels measured as a means of
distinguishing type 1 diabetes from type 2 diabetes or Maturity onset diabetes of
the young (MODY).
Clinical Usage of C peptide Measurement
- Measuring __-peptide can help to determine how much of their own natural
insulin a person is producing as C-peptide is secreted in ________ amounts to
_________.
- Measuring C-peptide can help to determine how much of their own natural
insulin a person is producing as C-peptide is secreted in equimolar amounts to
insulin.
Clinical Usage of C peptide Measurement
C-peptide levels are measured instead of _________ because C-peptide can
assess a person’s own _________ even if they receive _________ injections
C-peptide levels are measured instead of insulin levels because C-peptide can
assess a person’s own insulin secretion even if they receive insulin injections
Clinical Usage of C peptide Measurement
- Because the liver does not metabolize ____-peptide, meaning blood C-peptide may
be a better measure of ______ _______ secretion than insulin itself.
- Because the liver does not metabolize C-peptide, meaning blood C-peptide may
be a better measure of portal insulin secretion than insulin itself.
Clinical Usage of C peptide Measurement
A very low C-peptide confirms Type ____ diabetes and insulin ___________ and is
associated with high glucose variability, hyperglycaemia and increased
complications.
A very low C-peptide confirms Type 1 diabetes and insulin dependence and is
associated with high glucose variability, hyperglycaemia and increased
complications.
Hyperglycemia- recent increase in sugar levels not due to a underlying condition
Genetic Codon Change Causes Mutation in
Proteins
Point mutation
missense and nonsense mutation
- Point Mutations
– No change-silent due to alteration in 3rd base of
codon, wobble or degenerate base
– Missense- change in base leads to change in aa
– Nonsense-formation or modification of termination
codon
Genetic Codon Change Causes Mutation in
Proteins
Frameshift mutation
insertion or deletion of a nucleotide
Diseases Related to Mutations
a-thalassemia (Nonsense)
– normally 142 aa long
– If stop codon at 142 mutates get a 172 aa version including these
variants:
- Constant Spring: glutamine @ 142
- Icaria: lysine @ 142
- Seal Roe: glutamate @ 142
- Koya Dora: serine @ 142
- Thalassemia- Frameshift Mutation
Abnormal Hemoglobin Wayne
everything after 138 is incorrect (goes to 147
before stop)
Inhibitors of Protein Synthesis
Streptomycin and erythromycin
Streptomycin / Gentamycin: 30S prok. initiation
* Erythromycin: Target 50S prok. Elongation, both Gram + and Gram -
bacteria
Inhibitors of Protein Synthesis
Chloramphenicol and cyclohexamide
- Chloramphenicol: 70S ribosomal subunit in prok, elongation, broad
spectrum, bone marrow suppression - Cyclohexamide: 80S euk translocation step, and fungus etc
Inhibitors of Protein Synthesis
Tetracycline and Puromycin
- Tetracycline: Inhibits incoming tRNA to A site at 30S subunit in
prokaryotes - Puromycin: Premature terminator both prok and euk, mimic tRNA
binds at A site, resistant to hydrolysis
Inhibitors of Protein Synthesis
Diphtheria toxin
Euk elongation factor II inhibitor
Antibiotics Bind to Ribosome
The following antibiotics bind to the 30S subunit of the
ribosome:
– Aminoglycosides
– Tetracyclines
Antibiotics Bind to Ribosome
The following antibiotics bind to the 50S ribosomal subunit:
– Chloramphenicol
– Erythromycin
– Streptogramins- a group of cyclic peptide antibiotics that inhibit,
like macrolides and lincosamides, the synthesis of bacterial
proteins.
Streptogramins
a group of cyclic peptide antibiotics that inhibit,
like macrolides and lincosamides, the synthesis of bacterial
proteins.
Hemaglobulin Constant springs
Mutation at the stop codon at 142aa and gets elongated to a 172aa chain.
Glutamine @ 142
C peptide can be release in the blood and then
Get measured for a marker for Diabetic patients
Pre-pro- insulin sequence
Pre sequence
Has a lot of + charges of a single peptide sequence so it can go through the lipid bilayer
once it passes the bilayer the Pre sequence is removed
Pre-pro- insulin sequence
Pro sequence
This is where digestions and endonuclease cleavage happens into active insulin
Glycosylations of what molecular is common
Immunoglobulins
30s what does the S stand for
Size
Nonoverlapping
When mRNA is synthesized, it will read every three nucleotides without jumping
How two Aminoacids are linked
Carboxyl chain is linked to the N terminal with the removal of water
+ charged Amino acids
Lysine
Histidine
Arginine
Negative Charged Amino acids
Aspartic acid
Glutamic acid
AZT is used for patients with
AIDS and is where H-N-H binds to promotor regions and inhibits it
Rifampin is used to treat
Tuberculosis
Prokaryotes have almost no
modifications such as G-cap
Alternate splicing is where what is removed
Exons
Pre-mRNA is what
Introns and extrons but introns get removed
Splicing is
where introns are removed
Specific enzymes cut the primary transcript of mRNA, tRNA, and rRNA to make individual RNAs
Endonucleases
The promotor sequence is recognized by
RNA polymerase
The CAAT, GC, and TATA box are all located where
Upstream and are part of the promotor region and is toward the left side
Upstream of RNA
does not directly transcribe RNA but may regulate it
RNA is synthesized with only one strand of
DNA
Polymerase 3 is the main
Processive enzyme
P= Rho factor=
Stops synthesis= Rho dependent
SIgma subunit
Recognizes sequence in DNA template= promotor region
Cofactors for RNA synthesis
Mg2+, Fe2+, and Zn2+
RNA can be self folded into many shapes such as
Hair pin and step loop shaped
