Development of an expression system in E. coli for overproduction and proper post- translational modification of multiheme cytochromes c

Cytochromes c are electron transfer proteins containing one or more hemes covalently bound to the polypeptide chain. Not only are they widely used as models to address a number of issues (including electron transfer, apoptosis and protein folding) but they are also of interest in terms of development of expression protocols for proteins containing posttranslationally attached prosthetic groups. The major challenge during heterologous expression of cytochromes c is to provide proper post-translational modification of nascent polypeptide chains (heme attachment). In E. coli this can be achieved by targeting the apoprotein to the periplasm and coexpressing a group of auxiliary proteins (CcmABCDEFGH) responsible for cytochrome maturation under anaerobic conditions.