passages.id: split_6_test_1639_passage
passages.type: progene_text
passages.text: In this study , a system was developed for the production of heme - containing protein in a pure , recombinant holoprotein form , using the bovine cytochrome b5 tryptic fragment and Escherichia coli bacterioferritin as heterologous and homologous heme - containing model proteins , respectively .