Question

Which of the following best describes an amphipathic helix?

- a protein helix where the hydrophilic residues (usually negatively charged) and bulky hyrodrophobic residues (phe, ala and leu) are located on opposite helical faces.
-two cysteines and two histidines coordinated by a single zinc ion
-a DNA binding domain where two zinc ions are coordinated by 6 cysteines
-a triple helical cluster often stabilized by a beta sheet

Answer 1

An amphipathic helix in proteins has hydrophilic and hydrophobic residues on opposite sides, allowing integration into cell membranes. This structure is characterized by hydrophobic and hydrophilic faces, contributing to the protein's functionality.

Step-by-step explanation:

The amphipathic helix is a protein helix where the hydrophilic residues, often negatively charged, and the bulky hydrophobic residues like phenylalanine (Phe), alanine (Ala), and leucine (Leu) are located on opposite helical faces. Such a structure is able to integrate into cell membranes with the hydrophobic side facing the lipid core and the hydrophilic side facing the aqueous environment. This configuration helps facilitate various functions such as cellular transport or signal transduction.

Every helical turn in an alpha helix has 3.6 amino acid residues, with the R groups protruding out from the alpha-helix chain. The ß-pleated sheet, on the other hand, involves hydrogen bonding between atoms on the polypeptide chain backbone, with R groups attached to the carbons and extending above and below the folds. These structures are critical in contributing to the protein's three-dimensional shape and its functional capabilities.