Abstract
c-Type cytochromes are widespread proteins, fundamental for respiration or photosynthesis in most cells. They contain heme covalently bound to protein in a highly conserved, highly stereospecific post-translational modification. In many bacteria, mitochondria, and archaea this heme attachment is catalyzed by the cytochrome c maturation (Ccm) proteins. Here we identify and characterize a covalent, ternary complex between the heme chaperone CcmE, heme, and cytochrome c. Formation of the complex from holo-CcmE occurs in vivo and in vitro and involves the specific heme-binding residues of both CcmE and apocytochrome c. The enhancement and attenuation of the amounts of this complex correlates completely with known consequences of mutations in genes for other Ccm proteins. We propose the complex is a trapped catalytic intermediate in the cytochrome c biogenesis process, at the point of heme transfer from CcmE to the cytochrome, the key step in the maturation pathway.
Highlights
Heme attachment to cytochrome c is a catalyzed post-translational modification
We propose the complex is a trapped catalytic intermediate in the cytochrome c biogenesis process, at the point of heme transfer from CcmE to the cytochrome, the key step in the maturation pathway
Ternary complex between CcmE, heme, and cytochrome, and propose this represents a critical intermediate in the cytochrome c maturation (Ccm) pathway, at the point of heme transfer from the biogenesis system to the product cytochrome
Summary
Heme attachment to cytochrome c is a catalyzed post-translational modification. Results: We identify a ternary complex of the cytochrome c biogenesis protein CcmE, heme, and a cytochrome, and demonstrate its functional significance. C-Type cytochromes are widespread proteins, fundamental for respiration or photosynthesis in most cells They contain heme covalently bound to protein in a highly conserved, highly stereospecific post-translational modification. C-Type cytochromes are widespread proteins, essential for respiration and/or photosynthesis in mitochondria, chloroplasts, most bacteria, and some archaea They contain heme, covalently bound to the polypeptide chain. Binding motif (Fig. 1); the histidine becomes a ligand to the heme iron atom This heme attachment is a post-translational modification with strictly conserved stereospecificity [1]. CcmE is the pivotal protein in the Ccm system It binds heme covalently, through a histidine residue, as an intermediate in the cytochrome c biogenesis pathway (Fig. 1) [10].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
