Which family of proteins has the greatest likelihood of containing a Leucine-zipper motif?
Which family of proteins has the greatest likelihood of containing a Leucine-zipper motif?
Select an option to attempt
Correct Answer: Option C
Explanation
Leucine zipper motifs in transcription factors:Leucine zippers are dimerisation motifs in a class of transcription factors (bZIP family):Structure:• A stretch of ~4–5 LEUCINE residues spaced exactly 7 positions apart (every 2 turns of an-helix, since helices have 3.5 residues/turn).• These Leu residues are on the SAME face of the helix, forming a hydrophobic stripe.• Two such helices from partner proteins can interdigitate their leucine side chains (like a zipper closing) → coiled-coil dimer formation.• Adjacent to the leucine zipper is a basic region that contacts DNA (bZIP = basic Leucine Zipper).Examples of bZIP transcription factors:• c-Fos/c-Jun (AP-1 complex): oncoproteins• CREB (cAMP Response Element-Binding protein)• GCN4 (yeast) — the prototypical leucine zipper TFLeucine zippers are NOT found in serine proteases, MAP kinases, or sugar-binding proteins.Answer: Leucine zipper motifs are dimerisation domains found predominantly in bZIP transcription factors.