FIG 1.

Comparison of CcmC and CcsBA. (A) Schematic of H. hepaticus CcsBA topology. CcsBA consists of 10 transmembrane domains and a large periplasmic region. The following conserved features are shown: two conserved histidines in the transmembrane domain (TM-His1 and TM-His2) and two conserved periplasmic histidines (P-His1 and P-His2) which flank the heme-handling WWD domain. The site of natural proteolysis at residue 368 is indicated with an arrow. Conserved residues as defined in reference 3 are indicated in red. (Panel A is modified from reference 3 with permission from the publisher.) (B) Schematic of E. coli CcmC topology. CcmC consists of six transmembrane domains. An external heme binding domain consists of the WWD domain and two conserved histidines (P-His1 and P-His2). (Panel B is modified from reference 3 with permission from the publisher.) (C) Model of CcmC-heme-CcmE interaction. A structural model of CcmC (green) was generated using metagenomic coevolution data and experimentally determined constraints to position heme in the WWD domain (magenta). This model was docked with a known structure of CcmE. (Panel C is modified from reference 30 with permission from the publisher.)