Ann Taylor/HIV Protease

Function

Human Immunodeficiency Virus (HIV) is the cause of Acquired Immunodeficiency Syndrome (AIDS). HIV directs the synthesis of several polyproteins, which each consist of several tandemly linked proteins. The maturation of the virus to its infectious form requires that these polyproteins be cleaved to their component proteins. , a homodimeric enzyme, is responsible for doing so and is therefore crucial to the virus's infectious capacity.
HIV exists in two types HIV-1 and HIV-2. HIV-2 infects ca. 30% of AIDS patients vs. 70% infected by HIV-1^[1].
FIV is Feline Immunodeficiency virus protease.
SIV is Simian Immunodeficiency virus protease.

Structure of HIV-1 Protease

The X-ray structure of HIV-1 protease^[2][3] reveals that it is composed of , each consisting of 99 amino acid residues. The subunits come together in such as way as to . This tunnel is of critical importance because the active site of the protease is located in its interior. The active site consists of , making it a member of the aspartyl protease family. The two Asp's are either interact with the incoming water OR protonate the carbonyl to make the carbon more electrophilic for the incoming . You may be wondering how a polyprotein makes its way into the active-site tunnel, as the to admit it. The key is the two flexible flaps on the top of the tunnel that to enter the tunnel. The flaps , shifting from an open to a closed conformation to bind the target in an appropriate conformation for cleavage. This is more clearly seen at Flaps Morph for HIV Protease.