Structure and Function
HIV protease's protein structure has been investigated using X-ray crystallography. It exists as a homodimer, with each subunit made up of 99 amino acids.
The active site lies between the identical subunits and has the characteristic Asp-Thr-Gly (Asp25, Thr26 and Gly27) sequence common to aspartic proteases. The two Asp25 residues (one from each chain) act as the catalytic residues. According to the mechanism for HIV protease protein cleavage proposed by Mariusz Jaskolski and colleagues, water acts as a nucleophile, which acts in simultaneous conjunction with a well-placed aspartic acid to hydrolyze the scissile peptide bond. Additionally, HIV protease has two molecular "flaps" which move a distance of up to 7 Å when the enzyme becomes associated with a substrate.
Read more about this topic: HIV-1 Protease
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