Expression and purification of recombinant human PGRP-S. (A) Cell culture supernatant and cell lysates were tested for expression by Western blot with anti-His(C-term) antibody. (B) Coomassie Blue-stained 12% SDS-PAGE gel showing affinity-purified rhPGRP-S. Molecular markers are shown on the left. (C) Gel filtration chromatogram showing elution of rhPGRP-S from a Superdex 75HR column at a flow rate of 0.5 mL/min. Based on elution volumes of molecular weight standards, rhPGRP-S elutes as a monomer of approximately 23 kDa. (D) fast protein liquid chromatography (FPLC) fractions containing rhPGRP-S were subjected to 12% SDS-PAGE.