Final answer:
In the endoplasmic reticulum (ER), the form of HSP-70 used is the HSP70 protein. It acts as a chaperone, assisting in protein folding and trafficking within the ER.
Step-by-step explanation:
The form of HSP-70 that is used in the endoplasmic reticulum (ER) is specialized for assisting in the folding of proteins that are translocated into the ER lumen. In this context, HSP-70 works in conjunction with the signal recognition particle (SRP) and the SRP receptor to facilitate the translocation of secretory and membrane proteins into the ER. This is in line with the Signal Hypothesis, which explains that secretory proteins have an amino-terminal signal peptide that directs the polypeptide to the RER and, once it enters the RER, this signal peptide is cleaved off by signal peptidases. HSP-70 then aids in the proper folding of these nascent proteins to ensure they achieve their correct conformation for their biological function.