Influences of the heme-lysine crosslink in cytochrome P460 over redox catalysis and nitric oxide sensitivity
Ammonia (NH 3 )-oxidizing bacteria (AOB) derive total energy for life from the multi-electron oxidation of NH 3 to nitrite (NO 2 − ). One obligate intermediate of this metabolism is hydroxylamine (NH 2 OH), which can be oxidized to the potent greenhouse agent nitrous oxide (N 2 O) by the AOB enzyme...
Uloženo v:
| Vydáno v: | Chemical science (Cambridge) Ročník 9; číslo 2; s. 368 - 379 |
|---|---|
| Hlavní autoři: | , , |
| Médium: | Journal Article |
| Jazyk: | angličtina |
| Vydáno: |
England
Royal Society of Chemistry
2018
Royal Society of Chemistry (RSC) |
| Témata: | |
| ISSN: | 2041-6520, 2041-6539 |
| On-line přístup: | Získat plný text |
| Tagy: |
Přidat tag
Žádné tagy, Buďte první, kdo vytvoří štítek k tomuto záznamu!
|
| Shrnutí: | Ammonia (NH
3
)-oxidizing bacteria (AOB) derive total energy for life from the multi-electron oxidation of NH
3
to nitrite (NO
2
−
). One obligate intermediate of this metabolism is hydroxylamine (NH
2
OH), which can be oxidized to the potent greenhouse agent nitrous oxide (N
2
O) by the AOB enzyme cytochrome (cyt) P460. We have now spectroscopically characterized a 6-coordinate (6c) {FeNO}
7
intermediate on the NH
2
OH oxidation pathway of cyt P460. This species has two fates: it can either be oxidized to the {FeNO}
6
that then undergoes attack by NH
2
OH to ultimately generate N
2
O, or it can lose its axial His ligand, thus generating a stable, off-pathway 5-coordinate (5c) {FeNO}
7
species. We show that the wild type (WT) cyt P460 exhibits a slow nitric oxide (NO)-independent conversion (
k
His-off
= 2.90 × 10
−3
s
−1
), whereas a cross-link-deficient Lys70Tyr cyt P460 mutant protein underwent His dissociation
via
both a NO-independent (
k
His-off
= 3.8 × 10
−4
s
−1
) and a NO-dependent pathway [
k
His-off(NO)
= 790 M
−1
s
−1
]. Eyring analyses of the NO-independent pathways for these two proteins revealed a significantly larger (
ca.
27 cal mol
−1
K
−1
) activation entropy (Δ
S
‡
) in the cross-link-deficient mutant. Our results suggest that the Lys–heme cross-link confers rigidity to the positioning of the heme P460 cofactor to avoid the fast NO-dependent His dissociation pathway and subsequent formation of the off-pathway 5c {FeNO}
7
species. The relevance of these findings to NO signaling proteins such as heme-nitric oxide/oxygen binding (H-NOX) is also discussed. |
|---|---|
| Bibliografie: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 14 content type line 23 AC02-76SF00515; SC0013997 USDOE Office of Science (SC), Basic Energy Sciences (BES) |
| ISSN: | 2041-6520 2041-6539 |
| DOI: | 10.1039/C7SC03450D |