Heme c

Heme C differs from heme B in that the two vinyl side chains are covalently bound to the apoprotein itself through thioether linkages.

In addition to these covalent bonds, the heme iron is also usually coordinated to two side chains of amino acids, making the iron hexacoordinate. For example, cytochrome c contains a single heme C that is coordinated to side chains of both histidine and methionine. bc1 complex is another protein that contains a C type heme.

Some hemoproteins, often from single cell organisms, may contain up to four hemes C.

The correct structure of heme C was first published, in mid 20th century, by the Swedish biochemist K.-G. Paul.