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Why does sulfite reductase employ siroheme?

Brânzanic, Adrian M.V. ; Ryde, Ulf LU orcid and Silaghi-Dumitrescu, Radu (2019) In Chemical Communications 55(93). p.14047-14049
Abstract

Sulfite reductase (SiR) contains in the active site a unique assembly of siroheme and a [4Fe4S] cluster, linked by a cysteine residue. Siroheme is a doubly reduced variant of heme that is not used for a catalytic function in any other enzyme. We have used non-equilibrium Green's function methods coupled with density functional theory computations to explain why SiR employs siroheme rather than heme. The results show that direct, through vacuum, charge-transfer routes are inhibited when heme is replaced by siroheme. This ensures more efficient channelling of the electrons to the catalytic iron during the six-electron reduction of sulfite to sulfide, limiting potential side-reactions that could occur if the incoming electrons were... (More)

Sulfite reductase (SiR) contains in the active site a unique assembly of siroheme and a [4Fe4S] cluster, linked by a cysteine residue. Siroheme is a doubly reduced variant of heme that is not used for a catalytic function in any other enzyme. We have used non-equilibrium Green's function methods coupled with density functional theory computations to explain why SiR employs siroheme rather than heme. The results show that direct, through vacuum, charge-transfer routes are inhibited when heme is replaced by siroheme. This ensures more efficient channelling of the electrons to the catalytic iron during the six-electron reduction of sulfite to sulfide, limiting potential side-reactions that could occur if the incoming electrons were delocalized onto the macrocyclic ring.

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author
; and
organization
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type
Contribution to journal
publication status
published
subject
in
Chemical Communications
volume
55
issue
93
pages
3 pages
publisher
Royal Society of Chemistry
external identifiers
  • scopus:85075221789
  • pmid:31690895
ISSN
1359-7345
DOI
10.1039/c9cc05271b
language
English
LU publication?
yes
id
988a069d-1d68-4feb-a772-898b80f6bf92
date added to LUP
2019-12-10 08:50:14
date last changed
2024-08-07 11:09:08
@article{988a069d-1d68-4feb-a772-898b80f6bf92,
  abstract     = {{<p>Sulfite reductase (SiR) contains in the active site a unique assembly of siroheme and a [4Fe4S] cluster, linked by a cysteine residue. Siroheme is a doubly reduced variant of heme that is not used for a catalytic function in any other enzyme. We have used non-equilibrium Green's function methods coupled with density functional theory computations to explain why SiR employs siroheme rather than heme. The results show that direct, through vacuum, charge-transfer routes are inhibited when heme is replaced by siroheme. This ensures more efficient channelling of the electrons to the catalytic iron during the six-electron reduction of sulfite to sulfide, limiting potential side-reactions that could occur if the incoming electrons were delocalized onto the macrocyclic ring.</p>}},
  author       = {{Brânzanic, Adrian M.V. and Ryde, Ulf and Silaghi-Dumitrescu, Radu}},
  issn         = {{1359-7345}},
  language     = {{eng}},
  number       = {{93}},
  pages        = {{14047--14049}},
  publisher    = {{Royal Society of Chemistry}},
  series       = {{Chemical Communications}},
  title        = {{Why does sulfite reductase employ siroheme?}},
  url          = {{https://lup.lub.lu.se/search/files/84187867/259_siroheme.pdf}},
  doi          = {{10.1039/c9cc05271b}},
  volume       = {{55}},
  year         = {{2019}},
}