PMID:16824107

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Citation

Feissner, RE , Richard-Fogal, CL , Frawley, ER and Kranz, RG (2006) ABC transporter-mediated release of a haem chaperone allows cytochrome c biogenesis. Mol. Microbiol. 61:219-31

Abstract

Although organisms from all kingdoms have either the system I or II cytochrome c biogenesis pathway, it has remained a mystery as to why these two distinct pathways have developed. We have previously shown evidence that the system I pathway has a higher affinity for haem than system II for cytochrome c biogenesis. Here, we show the mechanism by which the system I pathway can utilize haem at low levels. The mechanism involves an ATP-binding cassette (ABC) transporter that is required for release of the periplasmic haem chaperone CcmE to the last step of cytochrome c assembly. This ABC transporter is composed of the ABC subunit CcmA, and two membrane proteins, CcmB and CcmC. In the absence of CcmA or CcmB, holo(haem)CcmE binds to CcmC in a stable dead-end complex, indicating high affinity binding of haem to CcmC. Expression of CcmA and CcmB facilitates formation of the CcmA2B1C1 complex and ATP-dependent release of holoCcmE. We propose that the CcmA2B1C1 complex represents a new subgroup within the ABC transporter superfamily that functions to release a chaperone.

Links

PubMed Online version:10.1111/j.1365-2958.2006.05221.x

Keywords

ATP-Binding Cassette Transporters/genetics; ATP-Binding Cassette Transporters/metabolism; Apoproteins/metabolism; Bacterial Outer Membrane Proteins/genetics; Bacterial Outer Membrane Proteins/metabolism; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Biological Transport; Cytochrome c Group/biosynthesis; Escherichia coli/genetics; Escherichia coli/metabolism; Escherichia coli Proteins/genetics; Escherichia coli Proteins/metabolism; Heme/metabolism; Hemeproteins/biosynthesis; Hemeproteins/genetics; Hemeproteins/metabolism; Membrane Proteins/genetics; Membrane Proteins/metabolism; Models, Biological; Molecular Chaperones/metabolism; Plasmids/genetics; Recombinant Fusion Proteins/metabolism

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