(A) Domains a, a0 and a′ (striped boxes), redox-active Trx domains; domain b (grey box), redoxinactive Trx domain; and domain c (white box), a putative calcium-binding domain. The C-terminal KEEL sequence is a possible ER-retention signal. (B) Detection of the mutants by the 5E phage antibody by Western blotting. Lane 1, marker proteins; lane 2, hPDIR-m1; lane 3, hPDIR-m3; lane 4, hPDIR-m2; lane 5, hPDIR-m12; lane 6, hPDIR-m13; lane 7, hPDIR-m23; lane 8, hPDIR-m123; lane 9, hPDIR-CGHS; lane 10, hPDIR-SGHC; lane 11, hPDIR-m12-GH; lane 12, hPDIR-m23-GH. hPDIR is shown in Figure 2. The 5E phage antibody (1011 pfu/ml) was used with each protein (approx. 5 μg).