Chapter 6, Problem 22CQ

(a)

Summary Introduction

To explain: The reason behind polar or charged residues usually appear in the remaining five positions in the polypeptide chain that form coiled coils

Concept introduction: The secondary structure is the formation of alpha helix and beta-pleated sheets. The α helix is formed when the peptide bond (C=O) of the nth residue along the helical axis points toward the peptide N-H group of the (n+4)th residue. β sheets are formed, when the hydrogen bonds between the parallel and anti-parallel strands of protein.

(b)

Summary Introduction

To explain: The reason behind the sequence Ile-Gln-Glu-Val-Glu-Arg-Arp is more likely than the sequence Trp-Gln-Glu-Tyr-Glu-Arg-Asp to appear in a coiled coil.

Concept introduction: The secondary structure is the formation of alpha helix and beta-pleated sheets. The residues at the first and fourth side chains of two helices usually form hydrophobic interacting surfaces that are buried in the core. α helix is formed when the peptide bond (C=O) of the nth residue points along the helical axis toward the peptide N-H group of the (n+4)th residue. β sheets are formed, when the hydrogen bonds between the parallel and anti-parallel strands of protein.