Fig. 4.

Summary of the components for disulfide bond formation in the bacterial periplasm, the endoplasmic reticulum (ER) and the mitochondrial intermembrane space (IMS). Each of the compartments where oxidative folding occurs is highlighted in dark blue. All three compartments have a similar layout and contain proteins with comparable functions. The main difference is present in the last column. The only compartment with a well-characterised reductive system is the periplasm. The ER has no known reductive pathway. In the IMS, the recent localisation of Grx2 and Trx1/Trr1 gives rise to a series of new questions concerning the characterization of a reductive pathway in this particular compartment