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).