Weaver eoc answers 12

Weaver eoc answers 12 - Answers to Weaver end of chapter...

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Answers to Weaver end of chapter questions Chapter 12 Transcription Activators in Eukaryotes 1. List three different classes of DNA-binding domains found in eukaryotic transcription factors. (a) zinc modules, (b) homeodomains, and (c) bZIP and bHLH motifs. 2. List three different classes of transcription activation domains in eukaryotic transcription factors. (a) acidic domains, (b) glutamine- rich domains, and (c) proline-rich domains. 3. Draw a detailed diagram of a zinc finger. Point out the DNA-binding motif of the finger. Refer to Fig. 12.1 and 12.2. Zinc fingers consist of an antiparallel β -strand, followed by an α - helix. Binding between the finger and its DNA binding site relies on direct amino acid-base interactions between amino acids in the α -helix and bases in the major groove of the DNA. 4. List one important similarity and three differences between a typical prokaryotic helix turn helix domain and the Zif268 zinc finger domain. Similarity: both domains bind to the DNA backbone and position the recognition helix for the best possible interaction with the DNA major groove. In particular, the α -helix in the zinc finger acts like the recognition helix in the helix-turn-helix domain in making specific contacts with the target DNA. Differences: (a) zinc finger proteins contain DNA binding domains that have a modular construction with several fingers making contact with the DNA. Thus these proteins have multiple DNA binding domains, wheras h-t-h proteins contain single domains, that often form multimers (dimers or tetramers) that bind the DNA. (b) With zinc-finger proteins most of the protein-DNA contacts are with one DNA strand, whereas, h-t-h containing proteins make contacts with both DNA strands. (c) With zinc finger proteins most of the protein-DNA contacts are amino acid side chain- DNA base interactions, rather than amino acid side chain-DNA backbone interactions. 5. Draw a diagram of the dimer composed of two molecules of the N-terminal 65 amino acids of the GAL4 protein, interacting with DNA. Your diagram should show clearly the dimerization domains and the motifs in the two DNA-binding domains interacting with their DNA binding sites. What metal ions coordinate amino acids, and how many of each, are present in each DNA binding domain? Refer to Fig. 12.4 in which three views of the GAL4-DNA complex are shown. DNA recognition module extends from amino acid residues 8-40, a linker region extends from residues 41-49, and the dimerization domain is comprised of residues 50-64. Each monomer contains a DNA binding motif with 6 cysteines that coordinate two zinc ions in a bimetal thiolate cluster. 6. In general terms, what is the function of a nuclear receptor?
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Nuclear receptors interact with endocrine and other signaling molecules, such as steroids and other hormones that diffuse through the cellular membrane. They act as hormone receptor complexes that bind to DNA sequence elements (enhancers) and function as transcriptional silencers or activators depending upon the presence of their cognate signaling molecule. 7.
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Weaver eoc answers 12 - Answers to Weaver end of chapter...

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