Download Translation and Proteins - HMartin

PowerPoint® Lecture Presentation for
Concepts of Genetics
Ninth Edition
Klug, Cummings, Spencer, Palladino
Chapter 15
Translation and Proteins
Lectures by David Kass with contributions from
John C. Osterman.
Copyright
© 2009©Pearson
Education,
Inc.
Copyright
2009 Pearson
Education,
Inc.
Central Dogma
http://cnx.org/content/m11415/latest/central_dogma.jpg
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Section 15.1
• Ribosomes
• consist of ribosomal proteins and ribosomal
RNAs (rRNAs).
• have a large subunit and a small subunit.
• The rRNAs provide for important catalytic
functions associated with translation.
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http://image.wistatutor.com/content/feed/u2044/ribosomes%20%20
function.jpg
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Figure 15.1
Section 15.1
• tRNAs
• 75–90 nucleotides long and contain
posttranscriptionally modified
bases.
• 2-dimensional structure of tRNAs is a
cloverleaf.
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Modified Bases (unusual bases)
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Figure 15.3
Section 15.1
• Aminoacyl
tRNA
synthetase
charges
(activates)
tRNAs with the
appropriate
amino acid.
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15.2Translation of mRNA Can Be
Divided into Three Steps
•
•
•
Initiation
Elongation
Termination
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Section 15.2
• Initiation requires:
•
•
•
•
•
the small and large ribosomal subunits
mRNA
GTP
charged initiator tRNA
initiation factors
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Figure 15.6
• Elongation requires
both ribosomal
subunits assembled
with the mRNA
to form the P
(peptidyl) site and
A (aminoacyl) site.
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Section 15.2
• Termination is
signaled by a stop
codon (UAG, UAA,
UGA) in the A site.
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Section 15.2
• Polysomes (or polyribosomes) are
mRNAs with several ribosomes translating
at once.
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Translation Is More Complex
in Eukaryotes
• In eukaryotes:
• the ribosomes are larger than in bacteria
• transcription and translation are spatially and
temporally separated
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Section 15.9
• Variation in Protein Structure Provides the
Basis of Biological Diversity
• Following translation, polypeptides fold up
and assume higher order structures, and
they may interact with other polypeptides.
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Section 15.9
• Amino acids all have:
•
•
•
•
a carboxyl group
an amino group
an R (radical) group bound
a central carbon atom
• The R group of an amino acid confers
specific chemical properties.
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Amino Acid Structure
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Figure 15.16
Section 15.9
• Peptide bond forms by a dehydration
reaction between the carboxyl group of one
amino acid and the amino group of another.
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Section 15.9
• There are 4 levels of protein structure:
• Primary
• Sequence of amino acids
• Secondary
• Tertiary
• Quaternary
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Secondary Structure
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Figure 15.18
Tertiary Structure
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Figure 15.19
Quaternary Structure
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Figure 15.20
Section 15.10
• Some proteins may be
posttranslationally modified.
• These modifications are crucial to the
functional capability of the final protein
product.
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15.11 Proteins Function in Many Diverse
Roles
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Section 15.12
• Protein molecules may have domains that
fold independently of the rest of the protein
into stable, unique conformations.
• Different protein domains impart different
functional capabilities.
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