PMID:12048216
| Citation |
Allen, JW, Tomlinson, EJ, Hong, L and Ferguson, SJ (2002) The Escherichia coli cytochrome c maturation (Ccm) system does not detectably attach heme to single cysteine variants of an apocytochrome c. J. Biol. Chem. 277:33559-63 |
|---|---|
| Abstract |
Cytochromes c are typically characterized by the covalent attachment of heme to polypeptide through two thioether bonds with the cysteine residues of a Cys-Xaa-Xaa-Cys-His peptide motif. In many Gram-negative bacteria, the heme is attached to the polypeptide by the periplasmically functioning cytochrome c maturation (Ccm) proteins. Exceptionally, Hydrogenobacter thermophilus cytochrome c(552), which has a normal CXXCH heme-binding motif, and variants with AXXCH, CXXAH, and AXXAH motifs, can be expressed as stable holocytochromes in the cytoplasm of Escherichia coli. By targeting these proteins to the periplasm using a signal peptide, with or without co-expression of the Ccm proteins, we have assessed the ability of the Ccm system to attach heme to proteins with no, one, or two cysteine residues in the heme-binding motif. Only the wild-type protein, with two cysteines, was effectively processed and thus accumulated in the periplasm as a holocytochrome. This is strong evidence for disulfide bond formation involving the two cysteine residues of apocytochrome c as an intermediate in Ccm-type Gram-negative bacterial cytochrome c biogenesis and/or that only a pair of cysteines can be recognized by the heme attachment apparatus. |
| Links |
PubMed Online version:10.1074/jbc.M204963200 |
| Keywords |
Amino Acid Motifs; Apoproteins/chemistry; Apoproteins/metabolism; Binding Sites; Cysteine; Cytochrome c Group/chemistry; Cytochrome c Group/metabolism; Cytochromes c; Escherichia coli/enzymology; Heme/metabolism |
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