Purification and characterization of endometrial protein PP14 from mid-trimester amniotic fluid

Abstract Two methods are described for the purification of placental protein 14 from human mid-trimester amniotic fluid. The first includes gel filtration, anion exchange chromatography, and reversed-phase high performance liquid chromatography. The second method employs octyl-Sepharose chromatography instead of high performance liquid chromatography, and it also includes an anti-hCG adsorption step in order to remove the remaining traces of hCG from the purified PP14. In the first method, 362 μg of PP14 was recovered from 26 ml amniotic fluid with a final recovery of 25%. In the second method, 745 μg of PP14 was recovered from 200 ml amniotic fluid with a final recovery of 9.8%. As a result of either method sodium dodecyl sulfate polyacrylamide gel electrophoresis of purified protein showed one band at 28 kDa. Polyclonal antibodies against placental PP14 reacted with this band in immunoblot analysis and radioimmunoassay. A single N-terminal amino acid sequence of MDIPQTKQDLELPKLAGTWHSMA was obtained for the isolated protein. This sequence is identical to that previously reported for human placental PP14. Due to its high PP14 concentration amniotic fluid serves as an excellent starting material for purification of this protein.