ISSN:
1617-4623
Keywords:
Key words Cytochrome c biosynthesis
;
Formate-dependent nitrite reduction
;
Nitritereduction
;
E. coli anaerobic metabolism
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract It has been suggested that two groups of Escherichia coli genes, the ccm genes located in the 47-min region and the nrfEFG genes in the 92-min region of the chromosome, are involved in cytochrome c biosynthesis during anaerobic growth. The involvement of the products of these genes in cytochrome c synthesis, assembly and secretion has now been investigated. Despite their similarity to other bacterial cytochrome c assembly proteins, NrfE, F and G were found not to be required for the biosynthesis of any of the c-type cytochromes in E. coli. Furthermore, these proteins were not required for the secretion of the periplasmic cytochromes, cytochrome c 550 and cytochrome c 552 , or for the correct targeting of the NapC and NrfB cytochromes to the cytoplasmic membrane. NrfE and NrfG are required for formate-dependent nitrite reduction (the Nrf pathway), which involves at least two c-type cytochromes, cytochrome c 552 and NrfB, but NrfF is not essential for this pathway. Genes similar to nrfE, nrfF and nrfG are present in the E. coli nap-ccm locus at minute 47. CcmF is similar to NrfE, the N-terminal region of CcmH is similar to NrfF and the C-terminal portion of CcmH is similar to NrfG. In contrast to NrfF, the N-terminal, NrfF-like portion of CcmH is essential for the synthesis of all c-type cytochromes. Conversely, the NrfG-like C-terminal region of CcmH is not essential for cytochrome c biosynthesis. The data are consistent with proposals from this and other laboratories that CcmF and CcmH form part of a haem lyase complex required to attach haem c to C-X-X-C-H haem-binding domains. In contrast, NrfE and NrfG are proposed to fulfill a more specialised role in the assembly of the formate-dependent nitrite reductase.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02173779
Permalink
