Recombinant human CRP (rhCRP) was secreted into culture supernatant of Escherichia coli by co-expressing kil gene that has a function to secrete colicin E 1 outside the cell. Highly purified 5 g rhCRP was produced from 180 L culture supernatant by affinity chromatography. The purified rhCRP was indistinguishable from the native one with respect to Ca2+-dependent binding ability to phosphorylcholine, electrophoretic behavior, N-terminal amino acid analysis, and immunochemical properties. The molecular weight of rhCRP monomer was determined to be 23059.7 Da by TOF/MS analysis. These results indicate that rhCRP has the same protein structure as native one and that rhCRP has the potential as a reference material and/or calibrator of high-sensitivity CRP assay to predict the risk of cardiovascular disease. (C) 2002 Elsevier Science (USA). All rights reserved.