Final answer:
Chaperonins have two substrate binding domain states, open and closed, which are interconverted with the help of ATP binding and hydrolysis at the ATP binding domain. This process is essential for proper protein folding and requires the coordinated function of both domains within the chaperonin complex.
Step-by-step explanation:
Chaperonins are a type of protein complex that assists in the proper folding of other proteins. The two forms of the substrate binding domain on a chaperonin are the open and closed states. During the open state, the substrate – an unfolded protein – can bind to the chaperonin. Once the substrate has bound, ATP binding occurs at the ATP binding domain, leading to a conformational change to the closed state where the substrate is tightly enclosed within the chaperonin. This change is critical for the proper folding of the substrate. The ATP binding and hydrolysis provide the energy necessary for the chaperonin to undergo cycles of opening and closing, allowing it to assist in protein folding through multiple rounds of substrate binding and release.
The proper function of both the substrate binding domain and the ATP binding domain are integral for the chaperonin's activity, as ATP binding and hydrolysis are directly connected to the substrate binding domain's ability to transition between its open and closed states. In essence, the energy from ATP hydrolysis drives the conformational changes necessary for substrate binding and release.