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Voiceover
HIV, the virus that causes AIDS, has many component proteins essential to its survival. The simple shapes in this model of HIV represent these proteins.

If scientists can find a way to inhibit the production of these proteins, then the progress of the virus could be slowed or stopped. The key to inhibiting this protein production may be found inside the virus itself.

The virus starts making these essential proteins by joining amino acids into long chains called pre-proteins. But these pre-proteins aren't yet biologically active.

A pre-protein must be cut apart to form biologically active proteins, like plastic trash bags that must be separated from their roll to be used.

A special kind of viral protein called a cleavage enzyme does this cutting of the pre-protein.

Cleavage enzymes are at work all around us. We can demonstrate one example using cow's blood. Thrombin is a cleavage enzyme for the pre-protein that leads to blood clots.

The thrombin we add to the small dish containing blood cuts the pre-protein into active clotting proteins.

These active proteins quickly form clots.

Discussion
The HIV-1 Protease: An Enzyme at Work video is not designed to be a stand-alone instructional tool. A teacher guide with student activities is available as a PDF file. Information and activities from this guide should supplement viewing and discussion of the video. Included in the guide are three student activities that use enzymes.

Note: Viewing and printing of the teacher guide requires Adobe Acrobat. A link for downloading the free Adobe Acrobat Reader software is on the CCA! Download page.