HIV-I protease is an enzyme produced by the HIV virus. Two identical chains of 99 amino acids form the enzyme. In each chain, amino acids 25, 25 and 27 in the sequence form part of the active site. Which orders of protein structure control the shape of the active site?

Explanation

We are told that we have 2 chains of amino acids that are forming the enzyme (since it is formed by 2 chains, we know it has a quaternary structure and the interaction between these two chains can have an effect on the active site. We are also told that the active site is located at specific numbers within the chain, meaning the order matters and primary structure will be involved. The last two structures we haven't mentioned are tertiary and secondary structures, and although they may not have anything that can specifically show their use in the text, we need to know that these two structures play key roles in the 3D shape of these polypeptides and how they assemble, therefore we cannot forget to include them. The 3D shape will influence how the active site is orientated and shaped, so we can confirm that secondary and tertiary will also play a role.