During mhc class i synthesis and folding in the endoplasmic reticulum (er), a process of peptide editing takes place as the newly synthesized mhc class i protein is held in a ‘peptide receptive’ state by binding to the calreticulin: erp57: tapasin complex. peptide editing
ensures that the mhc class i molecules that reach the cell surface have stable, high affinity binding for their peptide cargo. peptide
editing is important to the immune response because it:
a. maintains high levels of surface mhc class i expression
b. ensures that mhc class i molecules are not degraded in the er
c. retains the nascent mhc class i molecule in a peptide
receptive state
d. allows surface mhc class i molecules to bind new peptides
from the extracellular milieu
e. prevents surface mhc class i molecules from undergoing
peptide exchange at the cell surface