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.
Click on the interactive links in the text below.

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

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This molecule can be moved by holding down the left mouse button and dragging. The right button gives many options.
Start .. stop rotation
Click on the interactive links in the text below.

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)