Figure 8.

Model of oxidative protein folding by the multiple PDI family proteins/ERO1 system in plants. A, oxidative protein folding at a proper molar ratio of WT ERO1 to PDI family proteins. Oxidized PDI family proteins introduce disulfide bonds in unfolded protein (D_red) producing denatured protein with nonnative disulfide bonds (D_ox), and reduced PDI family proteins rearrange the disulfide bonds to the native ones, producing correctly folded native protein (N). Reduced PDI family proteins convert inactive ERO1 (ox-2) to the active form (ox-1). B, oxidative protein folding at an improperly high molar ratio of WT ERO1 to PDI family proteins. Oxidized PDI family proteins introduce disulfide bonds in D_red, and reduced PDI family proteins produce N. However, too many disulfide bonds beyond isomerization capacity of PDI family proteins are supplied by ERO1, resulting in part of D_red becoming denatured proteins with dead-end disulfides (D_end). C, oxidative protein folding at a proper molar ratio of hyperactive ERO1 to PDI family proteins. Many disulfide bonds within the limit of isomerization capacity of PDI family proteins are supplied by hyperactive ERO1 to D_red, resulting in D_red becoming N effectively. D, oxidative protein folding at an improperly high molar ratio of hyperactive ERO1 to PDI family proteins. Too many disulfide bonds are supplied by hyperactive ERO1, resulting in most of D_red becoming D_end. The number of copies of boxes are reflecting the relative concentration of the proteins.