Siroheme synthase orients substrates for dehydrogenase and chelatase activities in a common active site

Abstract

Siroheme is an essential bacterial iron tetrapyrrole used by siroheme-dependent sulfite and nitrite reductases. Here the authors shed light on the catalytic mechanisms of siroheme synthase through the structures of the bifunctional dehydrogenase/chelatase CysG module bound to its substrate, precorrin-2, the product/substrate sirohydrochlorin, and cobalt-sirohydrochlorin.