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Protein Translation
M. J. Chorney
Susquehanna MAGNET
November 11, 2013
Figure 6-50 Molecular Biology of the Cell (© Garland Science 2008)
The codons, RNA based
Figure 6-51 Molecular Biology of the Cell (© Garland Science 2008)
Open
Reading
Frames
revisited
Figure 6-98 Molecular Biology of the Cell (© Garland Science 2008)
Evolution of living organisms—an RNA beginning
Figure 6-101 Molecular Biology of the Cell (© Garland Science 2008)
RNA, single-stranded, can form structures due to base-pairing
Figure 6-99 Molecular Biology of the Cell (© Garland Science 2008)
Early RNA adapted the ability to perform enzymatic reactions
Figure 6-103 (part 1 of 3) Molecular Biology of the Cell (© Garland Science 2008)
Catalytically functional
RNAs are termed
Ribozymes—they
have been synthesized
in the laboratory
Figure 6-110 Molecular Biology of the Cell (© Garland Science 2008)
Evolution of cells and
dogma
Figure 6-52 Molecular Biology of the Cell (© Garland Science 2008)
tRNAs bring amino acids to the ribosomes, made
of rRNAs and proteins
Simple primary structure, complex
secondary and tertiary structure
Figure 6-55 Molecular Biology of the Cell (© Garland Science 2008)
Some unusual
bases of
tRNA
Figure 6-53 Molecular Biology of the Cell (© Garland Science 2008)
tRNA anticodon
Binds to mRNA codon;
the third position is
not required to be an
exact fit
Figure 6-56 Molecular Biology of the Cell (© Garland Science 2008)
ATP is the energy storage molecule
And it does a lot more—i.e. an
intermediate in conveying the
amino acid to the specific tRNA
Figure 6-57 Molecular Biology of the Cell (© Garland Science 2008)
Detail of the bond—again, a 3’-OH
Figure 6-58 Molecular Biology of the Cell (© Garland Science 2008)
Example of trp binding to its tRNA=charging
Figure 6-59 Molecular Biology of the Cell (© Garland Science 2008)
Synthetase
is the enzyme
adding the
a.a. to
the tRNA
Figure 6-60 Molecular Biology of the Cell (© Garland Science 2008)
Synthetase
and tRNA
Figure 6-61 Molecular Biology of the Cell (© Garland Science 2008)
ELONGATION and peptide bond formation, note amino and
carboxy termini
Figure 6-62 Molecular Biology of the Cell (© Garland Science 2008)
Ribosomes associated
with the endoplasmic
reticulum
Figure 6-63 Molecular Biology of the Cell (© Garland Science 2008)
RIBOSOMES
Large and small
subunits
Figure 6-64 Molecular Biology of the Cell (© Garland Science 2008)
Exit
Protein
Attach
Figure 6-65 Molecular Biology of the Cell (© Garland Science 2008)
mRNA
Figure 6-69b Molecular Biology of the Cell (© Garland Science 2008)
2o structure
Bacterial 50S
Figure 6-69a Molecular Biology of the Cell (© Garland Science 2008)
Ribbon figure of
50S subunit
protein
Figure 6-70 Molecular Biology of the Cell (© Garland Science 2008)
50S plus proteins, rotating
Figure 6-66 Molecular Biology of the Cell (© Garland Science 2008)
ELONGATION
revisited
Figure 6-67 Molecular Biology of the Cell (© Garland Science 2008)
Insuring fidelity, EF-TU
and EF-G in bacteria
(EF-1 and EF-2 in
eukaryotes)
Figure 6-21a Molecular Biology of the Cell (© Garland Science 2008)
Figure 6-72 Molecular Biology of the Cell (© Garland Science 2008)
INITIATION IN EUKARYOTES
Poly-A tail and cap protein
interaction with elF4G
Note, this
starts on the
40S subunit
attracting
the 60S
subunit
Figure 6-76 Molecular Biology of the Cell (© Garland Science 2008)
POLYRIBOSOME
Figure 6-74 Molecular Biology of the Cell (© Garland Science 2008)
TERMINATION AND
RELEASE FACTOR
Figure 6-77 Molecular Biology of the Cell (© Garland Science 2008)
SELENOCYSTEINE IS BOUND BY A SPECIAL tRNA
which uses the UGA stop codon
Table 6-4 Molecular Biology of the Cell (© Garland Science 2008)
Translation (i.e. ribosome) is a target of many antibiotics
Figure 6-79 Molecular Biology of the Cell (© Garland Science 2008)
Learning Objectives
1.Describe the concept of Wobble
2.Discuss the nature of RNA secondary and tertiary
structure as it relates to translation (t and r RNA)
3.Explain initation, elongation and termination in terms
of codon-anticodon recognition
4.Draw ATP; where does a 3’ hydroxyl fit into the trans-
lation mechanism?
5.Aminoacyl tRNA synthetase has an editing function:
Explain mechanisms to limit error in translation
Research Question
Alzheimer’s Disease is said to result from improper protein
folding and the creation of neurofibrillary tangles, or fibrils
that lead to plaque formation and neuronal loss. Beta-amyloid
protein plays a major part, with senilin, tau, Epo4E
and other proteins contributing. Provide evidence in support
of this statement—also consider early onset AD and the dominant
negative mutant of amyloid precursor protein gene.
The brain is susceptible to amyloidosis resultant from improper
protein folding. Briefly investigate prions and Huntington’s
disease (this latter disease results from a trinucleotide repeat
expansion and the creation of a gain of function mutation).