Question

The transcription factor AP-1 is a heterodimer consisting of c-jun and c-fos. C-jun and c-fos are soluble proteins that can be localized to either the cytosol or nucleus of a cell. C-jun and c-fos dimerize through a leucine zipper motif. In a leucine zipper motif, every 7 amino acid residues, or 2 full turns of an alpha helix, are leucine resides. Leucine and other amino acids on one face of the helix come together to form an opposite alpha helix that has a similar arrangement of leucine and other amino acids. Which solvent would be LEAST favorable for c-fos/c-jun dimerization?

a) hexane

b) ethanol

c) water

d) phosphate-buffered saline

the answer is hexane, but I can't figure out why. Please explain.

Answer 1

ANSWER:

leucine is hydrophobic in nature and carbon-hydrogen side chain. Therefore, if we use an hydrophobic solvent the leucine zipper would interact with both the opposite alpha helix and the solvent and will ultimately hinder the dimer creation. Thus, the least favourable solvent for c-fos/c-jun dimerization is hexane as it is the least polar and can interact with the hydrophobic face of the leucine zipper.