Purification and Structural Characterization of Human ERp29

ERp29 is a major resident of the endoplasmic reticulum (ER) and is postulated to play an important molecular chaperone role in most animal cells. Human ERp29 was isolated to homogeneity in high yield by using a bacterial expression system. Its secondary structure was studied by circular dichroism (CD), Fourier transformed infrared spectroscopy (FTIR) and Raman spectroscopy and it was found that human ERp29 comprises significant _-helical structure. The details of its temperature-induced conformational changes was studied by CD and FTIR for the first time, revealing that the protein is stable below 50 °C and has two distinct structural transitions between 50 °C and 70 °C. This may shed light on ERp29's inability to protect substrate proteins against thermal aggregation.