Levels of protein structure shown by the Insulin molecule

Amino acid colour codes: ASP, GLU, CYS, MET, LYS, ARG, SER, THR, PHE, TYR, ASN, GLN, GLY, LEU, VAL, ILE , ALA, TRP, HIS and PRO.

PRIMARY STRUCTURE

- amino acid sequence
The insulin molecule consists of 51 amino acid residues, in two chains. Initial scheme shows 764 atoms (ball and stick), coloured by elements. Highlight peptide bonds (-CONH-) between amino acids.
Show individual amino acids (coloured according to codes above): ball and stick / simple trace format.
Name / number / unlabel A chain residues
Name / number / unlabel B chain residues

SECONDARY STRUCTURE

- folding of polypeptide chain

Display A,B chains as ribbons
Cartoon format showing a helices red, sheets gold
Show / remove H bonds in main chains
Reset view

TERTIARY STRUCTURE

- 3-D shape, stabilised by bonds between sidechains

Dots on
/ off to display molecular surface
Display cysteines , show disulphide bridges
Show / remove sidechain H bonds

QUATERNARY STRUCTURE

- association (involving non-covalent bonds) of more than one polypeptide chain subunits to form a functional protein
The two-chain structure of insulin is not usually seen as the quaternary level since it is stabilised by disulphide bonds (and both chains came from a single polypeptide originally).
However, in the presence of mineral ions, insulin may associate to form dimers, tetramers etc. Zinc ions cause insulin to form into a stable hexamer (6 A & B chains). This hexameric form is found in beta-cells of the islets of Langerhans, and it is seen as helpful in prolonging the usefulness of insulin in treating diabetes.
Show hexameric form ... show zinc
This graphics display was prepared to support a unit on the levels of protein structure using insulin as an example.

Web references

Insulin From Wikipedia, the free encyclopedia

Crystallographic studies of modified insulin
Possibly relevant
material available online
(from Amazon.com)

Possibly relevant
material available online
(from Amazon.co.uk)