Proteins involved in transcription regulation exhibit special structural motifs
ID: 73037 • Letter: P
Question
Proteins involved in transcription regulation exhibit special structural motifs to bind DNA. Leucine zipper structures are found in a large number of transcription factors. The amino acid sequences of several leucinezipper and the structure of yeast leucine, zipper protein GCN4/DNA complex are shown below. How do leucine zipper proteins interact with DNA? What kind of noncovalent interactions might mediate the binding? What will happen if three of the conserved Arg residues in GCN4 are mutated to Glu? Explain. What is the function of the leucine zipper region of the protein? What will happen if you mutate all the leucine, residues to serine? Will this affect the DNA Zipper region binding? What is the length of the DNA binding region of GCN4 containing the sequence KRARNTEAARRSRARK and how does that compare with the diameter of a B-form DNA?Explanation / Answer
a. Leucine zipper recognizes palindromic sequences on DNA and bind with the help of stretch of positively charged leuciner residues.
Electrostatic interactions prevail between bZIP and DNA region.
If Glu is present in Leucine zipper, it will not bind to DNA as both DNA and Glu would carry negative charge and they would repel each other.
b. It is the positively charged amino acids so it binds to negatively charged phosphate of DNA.
Serine would reduce the strength of interaction as its uncharged amino acid. Specificity would also reduce.
Yes DNA binding will be affected. No specificity and no strong interaction due to uncharged amino acid.
c. Length of DNA binding region is usually a heptad sequence of leucine.
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