Question

This protein sequence forms an antiparallel coiled-coil. Place the peptides onto a helical wheel diagram and show which faces interact in the coiled-coil. Identify key interactions that stabilize the coiled-coil.

I L R L E R E I E D L Q K M K

Answer 1

Ans: Isoleucine (non polar), leucine (non polar), Arginine (+vely charged), leucine, Glutamate (-vely charged) , Arginine, Glutamate, Isoleucine, Glutamate, Aspertate (-vely charged), leucine, Glutamine (polar), Lysine (+vely charged), Methionine (non polar), Lysine

I L R L E R E I E D L Q K M K

From the sequence it is identified as leucine zipper. In which every seventh aminoacid is leucine, they interact hydrophobically and stabilise the coiled-coil. In the ring inner residues are coil 1 and outer residues are coil 2. I will start describing the sequence from left to right (from the second loop). KMKQLD forms coil 2. ILRLEREIE forms coil 1 these two coils interact by 4^th leucine on coil 1 (from left to right on the pepetide) and 11^th leucine on the 2^nd coil. Other than this DI (polar outerside of coil vs nonpolar innerside), RQ (uncharged slightly nonpolar innerside vs polar outerside of coil), EM (polar vs nonpolar), KR (both slightly polar), KL (slightly polar outerside of coil vs nonpolar innerside) interactions help the coiled coil stability