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.
Publication types
-
Comparative Study
-
Research Support, Non-U.S. Gov't
MeSH terms
-
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
Substances
-
ATP-Binding Cassette Transporters
-
Bacterial Outer Membrane Proteins
-
CcmA protein, bacteria
-
CcmB protein, E coli
-
CcmE protein, E coli
-
Escherichia coli Proteins
-
Hemeproteins
-
Protein Subunits
-
Aspartic Acid
-
Heme
-
Histidine
-
Adenosine Triphosphate
-
Cytochromes c
-
Lysine