Download Envr740 part 2

E. coli CAP +cAMP + DNA
HTH motif
cAMP
ATATAA = consensus
sequence of TATA box
start point at: Py2CA Py5
TFIID
Human TBP complexed at TATA
box of DNA
3
' A
T
A
T
A
C
G
T
A
T 5
'G
C
octamer
CAAT
GC
TATA
start point
DNA binding motif of steroid receptors
Zn fingers
Other DNA binding motifs
Helix-turn-helix
Helix-loop-helix
Additional motif often present in transcription factors
Leucine zippers
The zinc finger motif is:
-Cys-X2-4-Cys-X3-Phe-X5-Leu-X2-His-X3-His-
N-terminal
C-terminal
Zn finger fragment bound to DNA
Hormone binding and
dimerization regions
vary from 5-15%
GLUCOCORTICOID RECEPTOR FRAGMENT BOUND TO DNA
DNA binding
finger
N-terminal
C-terminal
dimerization
homeodomain
#2
#1
#3
#1, N-terminal
Helix-turn-helix binding motif
#3, C-terminal
bHLH DNA binding motif of transcription factor MyoD
helix 2
helix 1
basic region binding DNA
CREB-DNA complex
Leu selected in zipper
domain
Arg selected in DNA-binding
domain
Human protooncogenes c-Jun:c-Fos heterodimer
Chains: blue = c-Fos, green = c-Jun
Residues: red = Leu, purple = Arg
O
Keto-enol tautomerization
of Gua
N
HN O
O
H2NHN N
NN
HN
N
H2N
N
H2N
N
N
N
O
H
OH
O
NH
OH
N
N
N
O N
OH
N
N
N
keto form
H
N
N HN
N NN
N
N
2
(normal) H2N
N
N
H2N
N
H2N
N
N
HN
N
HN
N
2
N
enol form
N
2
H3C
O
OH
N
N
N
O
N
OH
H
N
HN
H
HN
N
O
OH
N
H
N
ON
H
pairing properties of enol
ON
N
NN
O HN
H
HN
N
N
N
N
One round of replication on mismatched
strands “fixes” the mutation.
GT  GC + AT
GT  GC + AT
Point mutation, transition
pyrimidinepyrimidine
purinepurine
Point mutation, transversion
GC  CG,
TA  AT,
GC  TA
pyrimidinepurine
purinepyrimidine
nonsense mutation occurs when a termination codon is generated
missense mutation occurs when a different amino acid is coded
Change of reading frame following the location of a deletion
ATA GCA ACC GGC CTT ACA AAT TC
ATA GCA ACC GCC TTA CAA ATT C
Mechanism for frameshift mutations
G-p
3'-G-p-G-p-G-p-G-p-G-p-G-5'
5'-C-p-C p-C-OH
3'-G-p-G-p G-p-G-p-G-p-G-5'
5'-C-p-C-p-C-OH
p-C
insertion
deletion
Bacterial nonsense suppressors
LOCUS
tRNA
WILD-TYPE
SUPPRESSOR
codon/anticodon
anticodon/codon
supD(su1)
Ser
UCG
CGA
CUA
UAG
supE(su2)
Gln
CAG
CUG
CUA
UAG
supF(su3)
Tyr
UAUC
GUA
CUA
UAG
supC(su4)
Tyr
AAUC
GUA
UUA
UAAG
supG(su5)
Lys
AAGA
UUU
UUA
UAAG
supU(su7)
Trp
UGG
CCA
UCA
UGAG
G
O
CH3
HN
O
O
HN
O
CH3
O
O
O
O
P O
O
O
O
thymine-thymine dimer
T
T