Midterm_WI13_Key

In the structure below circle the amphipathic alpha

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In the structure below, circle the amphipathic alpha helices ( red ) that stabilize the dimer and the basic regions ( green ) of the helices that interact with the DNA sugar phosphate backbone (4 pts)
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Two points for red circle, 2 for either or both greens. 6. Describe the A/B barrel motif. Where is the binding site located? Assist yourself with a diagram and be specific. (5 pts) a. Barrel made of beta alpha beta loops (1pt), with beta sheets on the inside (.5pt) and alpha helices on the outside (.5pt). The binding site is located between the C term of the beta sheet and the N term of the alpha helix - can also circle region, as in the picture (1.5pt). Drawing - any attempt at a barrel with beta sheets in the center and alpha helices on outside is OK (1.5pts): 7. a. Describe the protein motif known as the immunoglobin fold and assist yourself with a diagram (5pts) . Made of all beta strands - can also say (distorted) beta barrel (1pt). Contains disulfide bond(s) (1pt). Diagram below - Any attempt at drawing beta sheets in a barrel like manner is OK. Involved in antigen recognition/protein
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protein interaction (1 pt). Can have hypervariable loops (1pt). b. Which structural regions are involved in antigen recognition. Be specific (5pts). Hypervariable loops (3pts) in the variable domain of the immunoglobin molecule (2pts). c. In a class I MHC molecule, the extracellular portion consists of a peptide binding domain. Describe this structure and assist yourself with a diagram. Be specific (5 pts). Made of 2 alpha helices and beta sheets; 1 pt for mentioning the 2 alpha helices, .5 for the beta sheets. Can draw picture below for the points as well(1.5pts total). Residues projecting from the alpha helix stabilize foreign peptides (2pts total). Drawing with correct placement of peptide between helices (1.5pts )
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8. a. Use a diagram to describe the GroEL complex (2pts). 7 Units in one ring – 2 rings back to back –
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In the structure below circle the amphipathic alpha helices...

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