Contol of gene transcription
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Changes in gene expression underlie what?
The diversity of cell types in the body
All cells have the same … but different sets of …
Genes Proteins
What can affect which genes are expressed?
Responses to signals and other cues in the enviroment Cells also change gene expression in some disease states
What affects the level of translation?
The level of transcription in a cell High levels of transcription can mean more RNA is produced so more protein is made
What is the charge of DNA binding proteins?
They are positive
What is the target of DNA binding proteins?
The major groove
What is the charge of the phosphate backbone?
Negative
Unlike proteins, DNA has a limited what?
Topology
Regulatory proteins must recognise what on the DNA?
A specific nucleotide sequence
Why does the outisde of the helix contain information?
So that the double helix does not have to open
The edge of each pair is exposed at the surface, presenting a distinctive pattern of what?
H-bond acceptors H- bond donors Hydrogen atoms Methyl groups
Which groove is marked differently for each pair?
The major groove
Give the pattern of the major groove for: G-> C A- > T Know this to know the reverse
G to C H bond acceptor, H bond acceptor, H bond donor, Hydrogen atom A to T H bond acceptor, H bond donor, H bond acceptor Methyl group
Molecular recognition usually relies on what?
Exact fit between the two surfaces of a molecule
How do gene regulatory proteins recognise a specific DNA sequence?
The surface of the protein is complementary to the features of the double helix in that region
Proteins make a series of contacts using which 3 interactions?
Hydrogen bonds Ionic bonds Hydrophobic interactions
How are interactions between the proteins and DNA strong?
Even though each contact is weak, there are about 20 contacts making them hard to break
Where does ROX1 bind?
Known to bind to eight sites in three yeast genes
Do all the DNA binding sites have the same affinity for the ROX1 protein?
No
Describe the structure of a helix-turn-helix DNA binding motif
2 Alpha helices connected by a short constitute of amino acids The 2 alpha helixes are held at a fixed angle The more C terminal is called the recognition helix as it fits in to the major groove of DNA, making specific contacts
Helix-turn-helix proteins tend to bind as dimers to what?
Two consecutive major grooves
The DNA recognition site for Helix-turn-helix DNA binding motif is what?
Palindromic
Describe the structure of the zinc finger binding domain?
Four amino acids which hold the zinc atom Held by cis-cis-his-his Has three fingers
The alpha helix of the zinc finger can recognise how many bases?
Two