当前位置： SCI文献检索 > MOLECULAR MICROBIOLOGY期刊下所有文献 > The nrfI gene is essential for the attachment of the active site haem group of Wolinella succinogenes cytochrome c nitrite reductase.

The nrfI gene is essential for the attachment of the active site haem group of Wolinella succinogenes cytochrome c nitrite reductase.

Abstract：

:The cytochrome c nitrite reductase complex (NrfHA) is the terminal enzyme in the electron transport chain catalysing nitrite respiration of Wolinella succinogenes. The catalytic subunit NrfA is a pentahaem cytochrome c containing an active site haem group which is covalently bound via the cysteine residues of a unique CWTCK motif. The lysine residue serves as the axial ligand of the haem iron. The other four haem groups of NrfA are bound by conventional haem-binding motifs (CXXCH). The nrfHAIJ locus was restored on the genome of the W. succinogenes DeltanrfAIJ deletion mutant by integration of a plasmid, thus enabling the expression of modified alleles of nrfA and nrfI. A mutant (K134H) was constructed which contained a nrfA gene encoding a CWTCH motif instead of CWTCK. NrfA of strain K134H was found to be synthesized with five bound haem groups, as judged by matrix-assisted laser-desorption/ionization (MALDI) mass spectrometry. Its nitrite reduction activity with reduced benzyl viologen was 40% of the wild-type activity. Ammonia was formed as the only product of nitrite reduction. The mutant did not grow by nitrite respiration and its electron transport activity from formate to nitrite was 5% of that of the wild-type strain. The predicted nrfI gene product is similar to proteins involved in system II cytochrome c biogenesis. A mutant of W. succinogenes (stopI) was constructed that contained a nrfHAIJ gene cluster with the nrfI codons 47 and 48 altered to stop codons. The NrfA protein of this mutant did not catalyse nitrite reduction and lacked the active site haem group, whereas the other four haem groups were present. Mutant (K134H/stopI) which contained the K134H modification in NrfA in addition to the inactivated nrfI gene had essentially the same properties as strain K134H. NrfA from strain K134H/stopI contained five haem groups. It is concluded that NrfI is involved in haem attachment to the CWTCK motif in NrfA but not to any of the CXXCH motifs. The nrfI gene is obviously dispensable for maturation of a modified NrfA protein containing a CWTCH motif instead of CWTCK. Therefore, NrfI might function as a specific haem lyase that recognizes the active site lysine residue of NrfA. A similar role has been proposed for NrfE, F and G of Escherichia coli, although these proteins share no overall sequence similarity to NrfI and belong to system I cytochrome c biogenesis, which differs fundamentally from system II.

journal_name

Mol Microbiol

journal_title

Molecular microbiology

authors

Pisa R,Stein T,Eichler R,Gross R,Simon J

doi

10.1046/j.1365-2958.2002.02784.x

subject

Has Abstract

pub_date

2002-02-01 00:00:00

pages

763-70

issue

eissn

0950-382X

issn

1365-2958

pii

2784

journal_volume

pub_type

杂志文章

在线工具

The nrfI gene is essential for the attachment of the active site haem group of Wolinella succinogenes cytochrome c nitrite reductase.