4. Elastin, a muscle fiber protein, can assemble into fibers and disassemble dep

Question

4. Elastin, a muscle fiber protein, can assemble into fibers and disassemble depending on temperature. It assembles at higher temperatures and disassembles at lower temperatures. At higher temperatures, the change in free energy for the reaction, elastin --> elastin fibers, is negative for the reaction to proceed. Conversely, the free energy is positive at lower temperatures to allow for elastin fiber disassembly. Decide what the signs of the change in enthalpy and the change in entropy need to be. Explain how your choices account for the assembly of elastin at high temperature and its disassembly at low temperature. Assume that the change in enthalpy and the change in entropy are constant over this temperature range.

3. Consider the following protein sequence as an helix: Leu-Lys-Arg-Ile-Val-Asp-Ile-LeuSer-Arg-Leu-Phe-Lys-Val. How many turns does this helix make? Do you notice anything interesting about the arrangement of the amino acids when folded into an helix? Explain.

Explanation / Answer

3. As for one turn of alpha helix , 3.6 amino acids are responsible and the sequence contains 14 amino acids therefore there will be 4 turns in this protein.

You will notice that the polar and hydrophobic amino acids are spaced in such a way that all polar aminos are on one side or the helix and the hydrophobic are on the other side . Therefore, it's an amphipathic helix with hydrophobic side facing the proteins interior . If two or more such helices are present together they might wrap around each other .

Related Questions

Navigate

• Browse (All)
• Browse 4
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.