CrfP could be secreted from the cell. A Construction of the vector pSET-2-crfP-spa. B Western blot analysis of CrfP. Total cell proteins and secreted proteins extracted from strain ZY05719 with pSET-2-crfP-spa were probed with anti-FLAG serum and anti-GroEL serum. Only CrfP was present in the secreted proteins, but both GroEL and CrfP were present in the total cell proteins.