PROTOTYPE OF A HEME CHAPERONE ESSENTIAL FOR CYTOCHROME-C MATURATION

Heme, the iron-containing cofactor essential for the activity of many enzymes, is incorporated into its target proteins by unknown mechanism s. Here, an Escherichia coli hemoprotein, CcmE, was shown to bind heme in the bacterial periplasm by way of a single covalent bond to a hist idine. The heme was then released and delivered to apocytochrome c. Th us, CcmE can be viewed as a heme chaperone guiding heme to its appropr iate biological partner and preventing illegitimate complex formation.