Chapter 27: Protein structure

Chapter 27: Amino Acids, Peptides and Proteins

Protein Structure

Primary : the amino acid sequence, for example Bradykinin : Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg or, RPPGFSPFR.

Secondary : the conformational relationship of neighbouring amino acids : common substructures are a-helices (shown in red) and b-pleated sheets (shown in yellow), otherwise there are "random coils" (shown in grey).

C=O

N-H

a-helices

b-sheets

reset

Quaternary : some systems exist as larger "assemblies" several polypeptide chains.

The 3D CHIME image to the right shows all 8 of the polypeptide chains of human insulin.

The quaternary structure is a tetramer of subunits that each contains 2 polypeptides, A type (21 amino acids) and B type chains (30 amino acids).

The structure contains total of 204 amino acids.