Translation

Amino acids are assembled into a protein by 4 steps:
•  
•  
•  
•  

mRNA are responsible for carrying
information from genes
to produce  
in the  

rRNA
Associates with
 
to form 
for  

tRNA responsible for
 to ribosomes for
protein synthesis

Translation ‐> a process by which a   reads the sequence of   in a strand of mRNA and uses the information to produce a  from amino acids

Ribosomes are made up of   subunits

Prokaryotic –  S
‐ Large   + small  
‐ Contains   rRNA

Eukaryotic –  S
‐ Large ( S) + small ( S)

Each type of tRNA molecule carries  amino acids

All tRNAs fold into a complex 3‐D shape that looks like a  

Amino acid binding site for tRNA (at the  end) binds to the amino acid

Enzymes called   read the tRNA
sequence and add the appropriate amino acid to the stem

Anticodon loop is at  loop

An anticodon loop is a sequence of three bases that is   to a   in
the  . Each type of tRNA contains a different  

  is the family of enzymes that adds the amino acid to the tRNA ‐> “charging”

The  between an amino acid and its tRNA is determined at aminoacyl‐tRNA synthesis.

There are exactly   different aminoacyl‐tRNA synthetases in a cell.

ATP energy is used to add the amino acid to the   end.

The ribosome gets together with mRNA and the first tRNA so that translation can begin at the  

The complex first binds to the   and begins to scan to
find the start codon

  are proteins that help get the
ribosome/mRNA/tRNA assembled

The complex moves along the mRNA in the  

  binds to the small subunit and helps keep it apart from the
large subunit until the start codon is found

TEST QUESTION
If the ribosomes do not start at the of the mRNA, instead it binds to the , it will scan for a
specific nucleotide sequence

In prokaryotes called the  
In eukaryotes called the  

To stabilize and enhance the ribosomes during
translation, proteins bound to the  
interact with the  on the 

Poly(A) binding proteins AKA  
• PABPs (function) 

Ribosomes have  mRNA binding site and  binding sites for tRNAs

The ribosomal binding sites are
A (aminacyl site) =  
P (peptidyl site) = 
E (exit site) =  

The   forms the N‐terminus of the polypeptide

Having the tRNA go to the E site requires  

Termination occurs when a stop codon is reached  ,  ,   at the A site

Termination is recognized by proteins called  , which fit neatly into the  site (though they  

A single mRNA will bind several ribosomes and it will be called a  

The two types of polysomes are  and  

Membrane bound polysomes on the ER make  

After membrane bound polysomes are synthesized in the ER, they are transported to cell membrane or endosome via 

Free polysomes synthesize proteins needed by   and also  

The proteins synthesized by free polysomes travel to target by  

Most of a ribosome is comprised of   and the rest is made of  

rRNA molecules direct the   of protein synthesis

In order for ribosomes to be recruited, the   or   sequence must be recognized by 

What are the two thiings that initiation factors do?
1.  
2.  

Peptide elongation can be stoped by   that stops 

tRNA pools are suspectible to change in  

Which stop codon is the most efficent?

  can compete with release factors to bind stop codons
• possible if matching of  bases within the stop codon

Ribosome biogenesis can be regulated at  

Mutations of   are linked to ribosomopathy genetic diseases ‐> bone marrow failure syndromes, cancer, reduced red blood cells, and muscle wasting

The genetic code is  because
  in mRNA specify only  
amino acids and three nonsense codons
(stop codons)

Leucine is encoded by 

 mutations ‐> a change in the DNA
sequence that does not affect an amino
acid or protein

 ‐> a change in the DNA
sequence that results in a different amino
acid

 ‐> a change in the DNA
sequence that gives rise to a stop codon
rather than an amino acid

The last nucleotide of a codon can often
be changed with no effect on amino acid and is called  

Resistance to the antibiotics covered in class involves mutations of the   or mutations in
 .

What are 3 examples of antibiotics that selectively interact with 70s?

What are 2 antibitoics that irreversibly bind to 30s?

Cycloheximide: binds the ribosome and inhibits  ‐mediated translocation
• Blocks the   phase

TEST QUESTION: Puromycin: has a structure like that of the  
If binds to the   site and participates in peptide bond formation, it will produce peptidyl‐
puromycin and  

siRNA and miRNAs are involves in  regulation

Long RNAs are involved in  ,  , and  

RNAi uses siRNAs to do gene silencing that plays a role in  , , and  

  has become a valuable research and
medical tool since it allows the prevention of translation of
specific genes.

The RNA can act as a drug to target  
or restore  

Anti-microRNAs are chemically modifed, single stranded nucleic acids designed to specifically bind to and inhibit
  molecules

 work like a "bait" or titration so endogenous miRNA is not able to find mRNA