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Rhodobacter capsulatus magnesium chelatase subunit BchH contains an oxygen sensitive iron-sulfur cluster

Sirijovski, Nick LU ; Mamedov, Fikret LU ; Olsson, Ulf LU ; Styring, Stenbjörn LU and Hansson, Mats LU (2007) In Archives of Microbiology 188(6). p.599-608
Abstract
Magnesium chelatase is the first unique enzyme of the bacteriochlorophyll biosynthetic pathway. It consists of three subunits (BchI, BchD, and BchH). Amino acid sequence analysis of the Rhodobacter capsulatus BchH revealed a novel cysteine motif ((CX2CX3CX14C)-C-393) that was found in only six other proteobacteria (CX2CX3CX11-14C). The cysteine motif is likely to coordinate an unprecedented [Fe-S] cluster. Purified BchH demonstrated absorbance in the 460 nm region. This absorbance was abolished in BchH proteins with alanine substitutions at positions Cys396 and Cys414. These modified proteins were also EPR silent. In contrast, wild type BchH protein in the reduced state showed EPR signals resembling those of a [4Fe-4S] cluster with rhombic... (More)
Magnesium chelatase is the first unique enzyme of the bacteriochlorophyll biosynthetic pathway. It consists of three subunits (BchI, BchD, and BchH). Amino acid sequence analysis of the Rhodobacter capsulatus BchH revealed a novel cysteine motif ((CX2CX3CX14C)-C-393) that was found in only six other proteobacteria (CX2CX3CX11-14C). The cysteine motif is likely to coordinate an unprecedented [Fe-S] cluster. Purified BchH demonstrated absorbance in the 460 nm region. This absorbance was abolished in BchH proteins with alanine substitutions at positions Cys396 and Cys414. These modified proteins were also EPR silent. In contrast, wild type BchH protein in the reduced state showed EPR signals resembling those of a [4Fe-4S] cluster with rhombic symmetry and g values at 1.90, 1.93, and 2.09, superimposed with a [3Fe-4S] cluster centered at g = 2.02. The [3Fe-4S] signal was observed independently of the [4Fe-4S] signal under oxidizing conditions. Mg-chelatase activity assays showed that the cluster is not catalytic. We suggest that the [4Fe-4S] and [3Fe-4S] signals originate from a single coordination site on the monomeric BchH protein and that the [4Fe-4S] cluster is sensitive to oxidation. It is speculated that the cluster participates in the switching between aerobic and anaerobic life of the proteobacteria. (Less)
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author
organization
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type
Contribution to journal
publication status
published
subject
keywords
Xantha-f, Tetrapyrrole, Chlorophyll, Bacteriochlorophyll, chlH, Enzyme, Magnesium chelatase EC 6.6.1.1
in
Archives of Microbiology
volume
188
issue
6
pages
599 - 608
publisher
Springer
external identifiers
  • wos:000251407500006
  • scopus:36849009712
ISSN
0302-8933
DOI
10.1007/s00203-007-0282-1
language
English
LU publication?
yes
id
6867d86f-4bc5-40e1-ba88-89b27f02fd21 (old id 968716)
date added to LUP
2008-01-30 14:29:54
date last changed
2017-06-18 04:25:11
@article{6867d86f-4bc5-40e1-ba88-89b27f02fd21,
  abstract     = {Magnesium chelatase is the first unique enzyme of the bacteriochlorophyll biosynthetic pathway. It consists of three subunits (BchI, BchD, and BchH). Amino acid sequence analysis of the Rhodobacter capsulatus BchH revealed a novel cysteine motif ((CX2CX3CX14C)-C-393) that was found in only six other proteobacteria (CX2CX3CX11-14C). The cysteine motif is likely to coordinate an unprecedented [Fe-S] cluster. Purified BchH demonstrated absorbance in the 460 nm region. This absorbance was abolished in BchH proteins with alanine substitutions at positions Cys396 and Cys414. These modified proteins were also EPR silent. In contrast, wild type BchH protein in the reduced state showed EPR signals resembling those of a [4Fe-4S] cluster with rhombic symmetry and g values at 1.90, 1.93, and 2.09, superimposed with a [3Fe-4S] cluster centered at g = 2.02. The [3Fe-4S] signal was observed independently of the [4Fe-4S] signal under oxidizing conditions. Mg-chelatase activity assays showed that the cluster is not catalytic. We suggest that the [4Fe-4S] and [3Fe-4S] signals originate from a single coordination site on the monomeric BchH protein and that the [4Fe-4S] cluster is sensitive to oxidation. It is speculated that the cluster participates in the switching between aerobic and anaerobic life of the proteobacteria.},
  author       = {Sirijovski, Nick and Mamedov, Fikret and Olsson, Ulf and Styring, Stenbjörn and Hansson, Mats},
  issn         = {0302-8933},
  keyword      = {Xantha-f,Tetrapyrrole,Chlorophyll,Bacteriochlorophyll,chlH,Enzyme,Magnesium chelatase EC 6.6.1.1},
  language     = {eng},
  number       = {6},
  pages        = {599--608},
  publisher    = {Springer},
  series       = {Archives of Microbiology},
  title        = {Rhodobacter capsulatus magnesium chelatase subunit BchH contains an oxygen sensitive iron-sulfur cluster},
  url          = {http://dx.doi.org/10.1007/s00203-007-0282-1},
  volume       = {188},
  year         = {2007},
}