Final answer:
Beta2-microglobulin binding to MHC I heavy chains leads to the formation of the peptide-loading complex, which includes TAP, tapasin, calreticulin, ERp57, and PDI.
Step-by-step explanation:
When beta2-microglobulin binds to MHC I heavy chains (HCs), calnexin is indeed released. It then associates with TAP (transporter associated with antigen processing), tapasin, calreticulin, ERp57, and PDI (protein disulfide isomerase) to form what is known as the peptide-loading complex. This complex is essential in the process of antigen presentation, where it assists in the proper folding and loading of peptide antigens onto the MHC class I molecules before they are expressed on the cell surface to be recognized by T cells.