2.2 Lecture Flashcards
TATA box binding protein
which deforms the
DNA and acts as a scaffold for assembly of the transcriptional machinery
Where is the TATA box located?
located in the minor groove of DNA
How do alpha helices bind to DNA
alpha helices sit in the major groove, with helix side-
chains making nucleotide-specific contacts
The α helix diameter is 12Å, making it the perfect width to fit into the
major groove of DNA!
The function of the rest of the DNA-binding protein is to stably hold
the alpha helices in position to facilitate DNA binding
What kind of motifs do homeobox have?
-helix turn helix
- has 3 alpha helices
-recognition helix that binds to major groove of DNA
What does p53 do
p53 prevents cells with
damaged DNA from dividing
When DNA damage is too
great, p53 promotes cell death
p53 structure
-tetramer to 4 DNA major groove sites
-5 structural domains
-arginine residues causes tumors
How does arginine affect p53
Sequence-specific binding of nucleotides in the DNA major groove
Binding to sugar-phosphate backbone of the minor groove
(3) Stabilizing loop structure by facilitating zinc ion coordination
Interestingly, the mutations that most frequently are seen in cancers
are NOT in the residues involved in sequence-specific binding!
Cancer-associated mutations are in the arginines that bind the sugar-
phosphate backbone and that help coordinate the zinc ion
Zinc fingers
Coordinate a metal ion to stabilize protein folds
What does Cro do?
Lytic growth
Lambda repressor
Lysogenic growth
Cro and Lambda
Both positively regulate TRANSCRIPTION of their own gene and block TRANSCRIPTION of the other
Trp repressor
prevents TRANSCRIPTION of biosynthetic genes unless tryptophan levels are low
Lac repressor
-when lactose levels are high, repressor is taken off and degradation enzymes are TRANSCRIBED
-when lactose levels are low repressor is on and no degradation enzymes are transcribed
