C3: Trypsin (Serine Protease)

Trypsin is a digestive enzyme that is a member of a large class of enzymes that utilize a Ser residue to cleave esters as well as peptide bonds. Other examples of Serine proteases include chymotrypsin as well as elastase. The peptide backbone is shown in the Chime window on the left. The amino(N) and carboxy(C) termini are labeled.

The Scale of Things: How large is Trypsin? To find out do the following:
Select¬Mouse Click Action¬Toggle Distance Monitor
Now use the right mouse button to click on two atoms to find the distance between them. After you are done you probably want to reload the page by clicking in the left frame.

Secondary Structure: Is Trypsin largely helix or sheet? To find out try the following:
Select¬Change Color To¬Yellow
Did anything change color? Now try this:
Select¬Change Color To¬Yellow
Is Trypsin composed of mainly sheet or helix?

Catalytic Triad: Serine proteases have three residues that are critical for catalysis. These are a Ser195, His57, and Asp102 residue. It is difficult to select individual residues for display with Chime (however, this is easy for RasMol). You can try the following to get some idea of where these three residues are located:
Display¬Ball & Stick
Display¬Ball & Stick
Display¬Ball & Stick
You should now see ALL of the Asp, Ser, and His residues displayed! It is difficult to identify the three which belong to the triad. It might be helpful to display an inhibitor and color it yellow:
Display¬Ball & Stick
Select¬Change Color To¬Yellow
The catalytic triad can be more clearly seen by pressing the following button: .
If you want to see the catalytic triad in a pop-up, click here: