The Alternative Route to Heme in the Methanogenic Archaeon Methanosarcina barkeri
Figure 2
AhbA and AhbB from M. barkeri act as siroheme decarboxylase in vivo. (a) HPLC analysis of the tetrapyrroles accumulated in different E. coli strains. The HPLC analysis of cell free extracts from E. coli cells producing recombinant CysG (upper panel) shows the accumulation of siroheme (SH). In the presence of CysG and recombinant NirDLGH from Pseudomonas aeruginosa 12,18-didecarboxysiroheme (DDSH) is formed (middle panel). In the presence of CysG and recombinant AhbAB from M. barkeri DDSH is formed (lower panel). (b) Isotopic mass spectra of SH (upper panel) and DDSH (lower panel) after HPLC separation. Both SH and DDSH eluted from the column in their dilactone form probably due to oxidation during tetrapyrrole extraction.
