Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

The synthesis of the modified tetrapyrrole known as d(1) haem requires several dedicated proteins which are coded for by a set of genes that are often found adjacent to the structural gene, nirS, for cytochrome cd(1) nitrite reductase. NirE, the product of the first gene in the nir biogenesis operon, was anticipated to catalyse the conversion of uroporphyrinogen III into precorrin-2; this was confirmed, but it was shown that this enzyme is less sensitive to product inhibition than similar enzymes that function in other biosynthetic pathways. Sequence analysis suggesting that one of these proteins, NirN, is a c-type cytochrome, and has similarity to the part of cytochrome cd(1) that binds d(1), was validated by recombinant production and characterization of NirN. A NirN-d(1) haem complex was demonstrated to release the cofactor to a semi-apo form of cytochrome cd(1) from which d(1) was extracted, suggesting a role for NirN in the assembly of cytochrome cd(1) (NirS). However, inactivation of nirN surprisingly led to only a marginal attenuation of growth of Paracoccus pantotrophus under anaerobic denitrifying conditions. As predicted, NirC is a c-type cytochrome; it was shown in vitro to be an electron donor to the NirN-d(1) complex.

Original publication

DOI

10.1111/j.1742-4658.2009.07354.x

Type

Journal article

Journal

FEBS J

Publication Date

11/2009

Volume

276

Pages

6399 - 6411

Keywords

Anion Transport Proteins, Bacteria, Cytochromes, Escherichia coli Proteins, Heme, Nitrite Reductases, Paracoccus pantotrophus, Uroporphyrinogens, Uroporphyrins