Final answer:
GroEL can accommodate proteins up to about 60 kDa, HSP-70 generally interacts with peptides around 7 amino acids long and proteins around 70 kDa, and HSP-90 deals with even larger substrates, potentially exceeding 100 kDa. However, the exact size limits depend on several factors including the nature of the substrate and the conformational state of the chaperone.
Step-by-step explanation:
The question 'What is the size limit of GroEL? HSP-70 & HSP-90?' refers to the maximum size of substrates that chaperone proteins can accommodate. GroEL, also known as chaperonin, is part of a complex with GroES that assists in folding proteins. It has a cavity that can encapsulate proteins up to approximately 60 kDa in size. HSP-70 and HSP-90 are heat shock proteins that aid in protein folding, assembly, translocation, and degradation processes under both stress and non-stress conditions.
HSP-70 has a peptide-binding domain which binds to short stretches of hydrophobic amino acids, and can accommodate peptides of around 70 kDa, although it primarily binds to substrates of around 7 amino acids long during the folding process. HSP-90, on the other hand, tends to target larger, more complex proteins and has been shown to associate with substrates that have a broader range of molecular weights, which may exceed 100 kDa. Nonetheless, the precise size limit for substrates of HSP-70 and HSP-90 is conditional and based on the nature of the substrate as well as the chaperone's conformational state.