CP12 of Synechocystis can substitute for pea CP12 in the pea PRK/CP12/GAPDH complex. In vitro protein complex reconstitution assays were performed in DTT-reduced stroma preparations of isolated intact pea chloroplasts, adding either recombinant, His-tagged mature pea CP12 or Synechocystis CP12. After incubation, assays were chromatographed to metal ion affinity columns. Eluted proteins were, after SDS/PAGE, characterized by Western blot analysis using the indicated antisera.