Molecular chaperones are specialized cellular proteins that bind nonnative forms of other proteins and assist them to reach a functional conformation. The role of chaperone proteins under conditions of stress, such as heat shock, is to protect proteins by binding to misfolded conformations when they are just starting to form, preventing aggregation; then, following return of normal conditions, they allow refolding to occur. Chaperones also play essential roles in folding under normal conditions, providing kinetic assistance to the folding process, and thus improving the overall rate and extent of productive folding.
Mutations in the gene for StAR cause lipoid congenital adrenal hyperplasia (lipoid CAH), in which patients produce little steroid and can die shortly after birth. [ 9 ] Mutations that less severely affect the function of StAR result in nonclassic lipoid CAH or familial glucocorticoid deficiency type 3. [ 11 ] [ 12 ] All known mutations disrupt StAR function by altering its START domain. In the case of StAR mutation, the phenotype does not present until birth since human placental steroidogenesis is independent of StAR.