Education series - Discover Insulin

Everyday Proteins - Let's take a closer look at insulin

In our last blog, we learned how to to download a protein PDB file and convert it into a STL format suitable for 3D printing. Now here is your chance to start exploring the wonderful world of proteins. Let us print our first everyday protein - Insulin.

INSULIN

An essential hormone in our body that regulates carbohydrate and fat metabolism. Insulin is produced by cells in the pancreas called beta cells and is regulated in our body to ensure a balanced glucose levels. Too high or too low levels of glucose in our body can result in conditions known as hyperglycemia or hypoglycemia. 


Steps:
(1) Go to the protein database website (www.pdb.org)
(2) Search for 1TRZ
(3) Download the PDB file and follow steps from the previous tutorial
(4) Print your first insulin molecule and let's start exploring this fascinating molecule together

3D Printed View

Here is a 3D printed insulin molecule and pictures from front and back view.

Biochemistry

The insulin protein is made up of 51 amino acids, a relatively small protein with a molecular weight of 5808 Da. It is basically a dimer with an A-chain and B–chain covalently linked together by disulfide bonds. The primary structure of insulin was determined by Frederick Sanger in 1956 while the spatial conformation (tertiary structure) was found by Dorothy Hodgkin in 1969.

Structure

Fig. 1 Molecular view of insulin hexamer
(image source from Wikipedia)

In its native form, insulin is produced in the body by beta cells as a hexamer i.e. a unit consisting of six insulin molecules and has a zinc ion and histidine residues (highlighted in pink) holding the hexamer together (Fig. 1). The 3D printed model represents the molecule of human insulin obtained from the Protein Data Bank (PDB ID: 1TRZ); this structure is stabilized by three disulfide bonds.

Role in our body

Insulin plays an important in regulating glucose levels and fat metabolism in our body. Our body produces insulin to help cells in our body absorb glucose they need for energy production. Without insulin, cells in our body are unable to absorb the glucose they need and can cause high glucose levels in our bloodstream to reach toxic levels. Another function of insulin is to store sugar in our liver and releasing it when it is needed. Excess glucose in our body over a long-term can lead to hyperglycemia (high blood sugar).

Uses in Medicine

Patients suffering from diabetes may need to inject themselves with insulin to maintain appropriate glucose levels in their body. In most cases, these are type 1 diabetes patients who cannot produce insulin because the beta cells in their pancreas are damaged or dysfunctional so they need constant injections of insulin to help keep their glucose levels balanced. Therapeutic human insulin for clinical use is biosynthetically manufactured using recombinant DNA technology. The biosynthetic human insulin is of higher purity than those extracted from animals.

Reference

PDB ID: 1TRZ

E. Ciszak, G.D. Smith. Crystallographic evidence for dual coordination around zinc in the T3R3 human insulin hexamer. (1994) Biochemistry 33: 1512-17

You can now download the 3D STL file from Thingiverse 
http://www.thingiverse.com/thing:706311