Download Gene to Protein - April 27

DNA
Replication
Polymerase
DNA Pol III
(and I)
Monomers
dNTPs
Template
ssDNA
Direction of
synthesis
5’ to 3’
Product
polynucleotid
e
RNA
Transcription
Protein
Translation
DNA
Replication
Polymerase
DNA Pol III
(and I)
RNA
Transcription
RNA Pol
Monomers
dNTPs
NTPs
Template
ssDNA
ssDNA
Direction of
synthesis
5’ to 3’
Product
polynucleotid
e
5’ to 3’
polynucleotid
e
Protein
Translation
Fig. 17-7a-1
Promoter
Transcription unit
5
3
Start point
RNA polymerase
DNA
3
5
Fig. 17-7a-2
Promoter
Transcription unit
5
3
Start point
RNA polymerase
3
5
DNA
1
Initiation
5
3
Unwound
DNA
3
5
RNA
transcript
Template strand
of DNA
Fig. 17-7a-3
Promoter
Transcription unit
5
3
Start point
RNA polymerase
3
5
DNA
1
Initiation
5
3
3
5
RNA
transcript
Unwound
DNA
Template strand
of DNA
2 Elongation
Rewound
DNA
5
3
3
5
RNA
transcript
3
5
Fig. 17-7a-4
Promoter
Transcription unit
5
3
Start point
RNA polymerase
3
5
DNA
1
Initiation
5
3
3
5
RNA
transcript
Unwound
DNA
Template strand
of DNA
2 Elongation
Rewound
DNA
5
3
3
5
3
5
RNA
transcript
3 Termination
5
3
3
5
5
Completed RNA transcript
3
Fig. 17-7b
Nontemplate
strand of DNA
Elongation
RNA
polymerase
3'
RNA nucleotides
3' end
5'
5'
Direction of
transcription
(“downstream”)
Newly made
RNA
Template
strand of DNA
DNA
Replication
Polymerase
DNA Pol III
(and I)
RNA
Transcription
RNA Pol
Monomers
dNTPs
NTPs
Template
ssDNA
ssDNA
Direction of
synthesis
5’ to 3’
Product
polynucleotid
e
5’ to 3’
polynucleotid
e
Protein
Translation
Third mRNA base (3 end of codon)
First mRNA base (5 end of codon)
Fig. 17-5
Second mRNA base
the mechanism of translation
Amino
acids
Polypeptide
Ribosome
tRNA with
amino acid
attached
tRNA
Anticodon
Codons
5
mRNA
3
Fig. 17-14
3
Amino acid
attachment site
5
Hydrogen
bonds
Anticodon
(a) Two-dimensional structure
Amino acid
attachment site
5
3
Hydrogen
bonds
3
Anticodon
(b) Three-dimensional structure
5
Anticodon
(c) Symbol used
in this book
Aminoacyl-tRNA
synthetase (enzyme)
Amino acid
Attaching amino acids to tRNAs:
Amino-acyl tRNA synthases
P P P
Adenosine
ATP
-20 different synthases
-Require ATP
-Each must be specific to the right
amino acid and tRNA(s)
P
Adenosine
P Pi
Pi
P
i
tRNA
Aminoacyl-tRNA
synthetase
tRNA
P
Adenosine
AMP
Computer model
Aminoacyl-tRNA
(“charged tRNA”)
tRNAGLN
Aminoacyl-tRNA
synthase
(ATSGLN)
Adenylated Glutamine
Fig. 17-16b
P site (Peptidyl-tRNA
binding site)
E site
(Exit site)
A site (AminoacyltRNA binding site)
E P A
mRNA
binding site
Large
subunit
Small
subunit
(b) Schematic model showing binding sites
Growing polypeptide
Amino end
Next amino acid
to be added to
polypeptide chain
mRNA
5
E
tRNA
3
Codons
(c) Schematic model with mRNA and tRNA
The Ribosome
LSU
SSU
Fig. 17-18-1
Amino end
of polypeptide
E
3
mRNA
5
P
A
site site
Fig. 17-18-2
Amino end
of polypeptide
E
3
mRNA
5
P
A
site site
GTP
GDP
E
P A
Fig. 17-18-3
Amino end
of polypeptide
E
3
mRNA
P
A
site site
5
GTP
GDP
E
P A
E
P A
Peptide bond formation
- Transfer of growing chain from tRNA
in P site to tRNA in A site
Fig. 17-18-3
Amino end
of polypeptide
E
3
mRNA
P
A
site site
5
GTP
GDP
E
P A
E
P A
Fig. 17-18-4
Amino end
of polypeptide
E
3
mRNA
Ribosome ready for
next aminoacyl tRNA
P
A
site site
5
GTP
GDP
E
E
P A
P A
GDP
GTP
E
P A
Fig. 17-17
Initiating translation
3 U A C 5
5 A U G 3
Initiator
tRNA
Large
ribosomal
subunit
P site
GTP
GDP
E
mRNA
5
Start codon
mRNA binding site
3
Small
ribosomal
subunit
5
A
3
Translation initiation complex
Fig. 17-19-1
Terminating translation
Release
factor
3
5
Stop codon
(UAG, UAA, or UGA)
Fig. 17-19-2
Terminating translation
Release
factor
Free
polypeptide
3
5
5
Stop codon
(UAG, UAA, or UGA)
3
2
GTP
2 GDP
Fig. 17-19-3
Terminating translation
Release
factor
Free
polypeptide
5
3
5
5
Stop codon
(UAG, UAA, or UGA)
3
2
GTP
2 GDP
3
Fig. 17-20
Growing
polypeptides
Completed
polypeptide
Incoming
ribosomal
subunits
Start of
mRNA
(5 end)
(a)
End of
mRNA
(3 end)
Ribosomes
mRNA
(b)
0.1 µm
Fig. 17-24
RNA polymerase
DNA
In bacteria:
Translation can
happen while
transcription is still
ocurring
mRNA
Polyribosome
RNA
polymerase
Direction of
transcription
0.25 µm
DNA
Polyribosome
Polypeptide
(amino end)
Ribosome
mRNA (5 end)
Fig. 18-3a
In bacteria: Many genes are organized in operons
Operon = group of genes sharing one promoter, expressed as 1 mRNAs
containing multiple ORFs
trp operon
Promoter
Genes of operon
trpE
Start codon
mRNA 5
E
trpD
trpC
trpB
trpA
B
A
Stop codon
D
C
Polypeptide subunits that make up
enzymes for tryptophan synthesis
DNA
Replication
Polymerase
DNA Pol III
(and I)
Protein
RNA
Transcription
RNA Pol
Translation
ribosome
Monomers
dNTPs
NTPs
Aminoacyl-tRNAs
Template
ssDNA
ssDNA
mRNA
Direction of
synthesis
5’ to 3’
Product
polynucleotid
e
5’ to 3’
polynucleotid
e
N to C
polypeptide