42. (6 points) The catalytic subunit of the muscle calcium ATPase pump has ten transmembrane alpha helices. The C-terminus is on the cytoplasmic face of the plasma membrane. Make a line drawing of the protein in the membrane (like in the PowerPoint lecture notes). Clearly label the N and C termini and all internal-signal-anchor II (2), internal-signal-anchor III (3) and stop-transfer-anchor (S) sequences, then answer the questions below: cytoplasmic face ___________________________________________________________________ ER membrane exoplasmic face ____________________________________________________________________ _______ Are positively charged (basic) amino acids clustered on the N-side or the C-side of the first transmembrane alpha helix? _______ How many internal-signal-anchor II sequences are present? _______ How many internal-signal-anchor III sequences are present? _______ How many stop-transfer-anchor sequences are present?
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Since this is a text-based platform, I can't draw a picture, but I can describe it. Imagine a horizontal line representing the plasma membrane. The protein, with its ten transmembrane alpha helices, is embedded in this line. The N-terminus is on the top Show more…
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34 If you were reading off the sequence of amino acids in the figure to a biologist friend, what should the first three letters be? A) M-N-G B) A-P-A C) It does not matter, since the protein has no polarity or directionality. 35 Identify the location of the disulfide bond in the figure, located at the bottom of the third transmembrane segment. What is the name of the amino acids that are forming this bond? A) cytosine B) aspartic acid C) cysteine D) glycine 36 What is the location of the C-terminus of the protein in the figure? A) extracellular B) cytoplasm C) embedded within the membrane D) nucleus 37 Refer to the figure. Which level of structure is maintained by the disulfide bond? A) primary B) secondary C) tertiary D) quaternary
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5A. (6 points) Use the helical wheel diagram shown here to determine the distribution of amino acid residues in a helical segment with the sequence: -Val-Asp-Arg-Val-Phe-Ser-Asn-Val-Cys-Thr-His-Leu-Lys-Thr-Leu-Gln-Asp-Lys- 5B. (3+2=5 points) Is this helix most likely part of an integral membrane protein, or a peripheral protein, or an amphitropic protein? Explain briefly. 5C. (2+3=5 points) Relatively speaking, which of the two molecules (water or alanine amino acid) can diffuse across a cell membrane with more ease than the other? Why?
The transmembrane regions of integral membrane proteins tend to fold into regular, repeating secondary structural elements. a. Given what you know about the forces that drive protein folding, provide an explanation for this observation. b. Why might a single beta strand not be very stable as a transmembrane segment. c. A transmembrane segment of an integral membrane protein contains two Asn, three Gln, and one Ser residue. If this segment folds into an alpha helix, predict the positions along the linear protein chain that these residues might occupy. (For example, N-X-X-Asn-X-X-X…… -C where X is any other sidechain residue.) Briefly explain your answer.
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