Isolation and partial characterization of rat liver porphyrin binding proteins

14C-coproporphyrin III was added to hemoglobin-free cytoplasmic rat liver extract. Molecular sieving was performed on Sephadex G-75 column. The protein content of each fraction was measured at 280 nm in double beam spectrophotometer and the radioactivity by means of liquid scintillation counter. In several runs on Sephadex we found four main radioactive peaks which correlate to four porphyrin binding proteins in rat liver cytoplasm. One fraction, which probably is identical with Y protein or ligandin, was further purified and characterized by means of different chromatographic techniques.