Final answer:
The exact amount of ATP hydrolyzed during protein degradation by the proteasome varies with the process involving multiple ATP-dependent steps, such as ubiquitin activation, protein polyubiquitination, and unfolding before and during proteasomal degradation.
Step-by-step explanation:
The number of ATP molecules that must be hydrolyzed by the proteasome for the digestion of a protein tagged with a polyubiquitin chain can vary. The ubiquitin-proteasome pathway is a multistep process that requires ATP in several stages, beginning with the activation of ubiquitin, continuation with polyubiquitination of the target protein, and the unfolding and translocation of the target protein into the proteasome.
Hydrolysis of ATP provides the energy for these steps. Specific numbers of ATPs used can depend on the length and configuration of the ubiquitin chain and the nature of the substrate protein. Once the target protein is unfolded and translocated into the core of the proteasome, it is digested into short peptide fragments, which are then broken down to free amino acids in the cytoplasm.