Around 75, 000 (as of February 2012) proteins have a known structure. They can be found on " Protein Data Bank ".  PDB

  which, in June 2004, only counted :
25 000

All these proteins play a key role in Biology. An increasing number of them are medicines

click on the eye to have a look
Proteins are chains of amino acids, such as glycine, arginine, etc... There are 20 of them. If you want to access their structure & how they are symbolized,  click here