(8) Estimate the net charge of the following peptide at pH 7 and pH 12: Ser-Glu-Pro-Ile-Met-Ala-Pro-Val-Glu-Tyr-Pro-Lys pH7 (+) (-) (-) (+) (-) NET= -1 pH12 (-) (-) (-) (-) NET= -4 (9) The C-terminal region of the enzyme adenylate kinase forms an α-helical and has the following amino acid sequence: Val-Asp-Asp-Val-Phe-Ser-Gln-Val-Cys-Thr-His-Leu-Asp-Thr-Leu-Lys- (a) Assume that the helix contributes residues to the hydrophobic core of the protein. Indicate which of the residues in the helix you expect to be projected into the core of the globular protein. Explain your answer. Val-Asp-Asp-Val-Phe-Ser-Gln-Val-Cys-Thr-His-Leu-Asp-Thr-Leu-Lys Residues expected to be projected into the core are underlined. If they are in alpha helix I expect hydrophobic residues positioned 3-4 amino acids apart to be on same face of the helix. This face of the helix projects the side chains into the core of the protein. [see handout for helical wheel] (b) What effects do proline and glycine have on the stability of α-helix? These residues tend to destabilize alpha helices.(10) The following amino acid sequence corresponds to one strand in an anti parallel beta. Assume that residues in the strand are part of the hydrophobic core of the protein. Indicate which of residues in the strand you expect to be projected into the core of the globular protein. Explain your answer. GLU-VAL-LYS-TYR-ARG-LEU-ASN-ALA-ILE-VAL-ASP-MET-SER-PHE Answer: GLU-VAL-LYS-TYR-ARG-LEU-ASN-ALA-ILE-VAL-ASP-MET-SER-PHE Residues expected to be projected into the core are underlined. In beta strands the side chain of every other residue faces to the same side of the beta sheet. Selecting the above residues includes the largest number of hydrophobic residues. (See Figure 6-7 for structural
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