PMID:17419738

Citation	Christensen, O, Harvat, EM, Thöny-Meyer, L, Ferguson, SJ and Stevens, JM (2007) Loss of ATP hydrolysis activity by CcmAB results in loss of c-type cytochrome synthesis and incomplete processing of CcmE. FEBS J. 274:2322-32
Abstract	The proteins CcmA and CcmB have long been known to be essential for cytochrome c maturation in Escherichia coli. We have purified a complex of these proteins, and found it to have ATP hydrolysis activity. CcmA, which has the features of a soluble ATP hydrolysis subunit, is found in a membrane-bound complex only when CcmB is present in the membrane. Mutation of the Walker A motif in CcmA(K40D) results in loss of the in vitro ATPase activity and in loss of cytochrome c biogenesis in vivo. The same mutation does not prevent covalent attachment of heme to the heme chaperone CcmE, but holo-CcmE is, for some unidentified reason, incompetent for heme transfer to an apocytochrome c or for release into the periplasm as a soluble variant. Addition of exogenous heme to heme-permeable E. coli with a ccmA deletion did not restore cytochrome c production. Our results suggest a role for CcmAB in the handling of heme by CcmE, which is chemically complex and involves an unusual histidine-heme covalent bond.
Links	PubMed Online version:10.1111/j.1742-4658.2007.05769.x
Keywords	ATP-Binding Cassette Transporters/biosynthesis; ATP-Binding Cassette Transporters/chemistry; ATP-Binding Cassette Transporters/genetics; ATP-Binding Cassette Transporters/metabolism; Adenosine Triphosphate/metabolism; Amino Acid Motifs/genetics; Aspartic Acid/genetics; Bacterial Outer Membrane Proteins/biosynthesis; Bacterial Outer Membrane Proteins/chemistry; Bacterial Outer Membrane Proteins/genetics; Bacterial Outer Membrane Proteins/metabolism; Cytochromes c/biosynthesis; Cytochromes c/genetics; Cytochromes c/metabolism; Escherichia coli/enzymology; Escherichia coli/genetics; Escherichia coli Proteins/biosynthesis; Escherichia coli Proteins/genetics; Escherichia coli Proteins/metabolism; Heme/metabolism; Hemeproteins/biosynthesis; Hemeproteins/genetics; Hemeproteins/metabolism; Histidine/metabolism; Hydrolysis; Lysine/genetics; Mutagenesis, Site-Directed; Protein Processing, Post-Translational/genetics; Protein Subunits/chemistry; Protein Subunits/genetics; Protein Subunits/metabolism; Sequence Deletion
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