PMID- 35120924
OWN - NLM
STAT- MEDLINE
DCOM- 20220415
LR  - 20220531
IS  - 1083-351X (Electronic)
IS  - 0021-9258 (Print)
IS  - 0021-9258 (Linking)
VI  - 298
IP  - 3
DP  - 2022 Mar
TI  - Molecular mechanism of intramolecular electron transfer in dimeric sulfite 
      oxidase.
PG  - 101668
LID - S0021-9258(22)00108-9 [pii]
LID - 10.1016/j.jbc.2022.101668 [doi]
LID - 101668
AB  - Sulfite oxidase (SOX) is a homodimeric molybdoheme enzyme that oxidizes sulfite 
      to sulfate at the molybdenum center. Following substrate oxidation, molybdenum is 
      reduced and subsequently regenerated by two sequential electron transfers (ETs) 
      via heme to cytochrome c. SOX harbors both metals in spatially separated domains 
      within each subunit, suggesting that domain movement is necessary to allow 
      intramolecular ET. To address whether one subunit in a SOX dimer is sufficient 
      for catalysis, we produced heterodimeric SOX variants with abolished sulfite 
      oxidation by replacing the molybdenum-coordinating and essential cysteine in the 
      active site. To further elucidate whether electrons can bifurcate between 
      subunits, we truncated one or both subunits by deleting the heme domain. We 
      generated three SOX heterodimers: (i) SOX/Mo with two active molybdenum centers 
      but one deleted heme domain, (ii) SOX/Mo_C264S with one unmodified and one 
      inactive subunit, and (iii) SOX_C264S/Mo harboring a functional molybdenum center 
      on one subunit and a heme domain on the other subunit. Steady-state kinetics 
      showed 50% SOX activity for the SOX/Mo and SOX/Mo_C264S heterodimers, whereas 
      SOX_C264S/Mo activity was reduced by two orders of magnitude. Rapid reaction 
      kinetics monitoring revealed comparable ET rates in SOX/Mo, SOX/Mo_C264S, and 
      SOX/SOX, whereas in SOX_C264S/Mo, ET was strongly compromised. We also combined a 
      functional SOX Mo domain with an inactive full-length SOX R217W variant and 
      demonstrated interdimer ET that resembled SOX_C264S/Mo activity. Collectively, 
      our results indicate that one functional subunit in SOX is sufficient for 
      catalysis and that electrons derived from either Mo((IV)) or Mo((V)) follow this 
      path.
CI  - Copyright (c) 2022 The Authors. Published by Elsevier Inc. All rights reserved.
FAU - Eh, Malin
AU  - Eh M
AD  - Department of Chemistry, Institute of Biochemistry, University of Cologne, 
      Cologne, Germany.
FAU - Kaczmarek, Alexander Tobias
AU  - Kaczmarek AT
AD  - Department of Chemistry, Institute of Biochemistry, University of Cologne, 
      Cologne, Germany.
FAU - Schwarz, Guenter
AU  - Schwarz G
AD  - Department of Chemistry, Institute of Biochemistry, University of Cologne, 
      Cologne, Germany. Electronic address: gschwarz@uni-koeln.de.
FAU - Bender, Daniel
AU  - Bender D
AD  - Department of Chemistry, Institute of Biochemistry, University of Cologne, 
      Cologne, Germany; Department of Pediatric Neurology, University Children's 
      Hospital Zurich, Zurich, Switzerland. Electronic address: 
      daniel.bender@kispi.uzh.ch.
LA  - eng
PT  - Journal Article
DEP - 20220202
PL  - United States
TA  - J Biol Chem
JT  - The Journal of biological chemistry
JID - 2985121R
RN  - 0 (Sulfites)
RN  - 42VZT0U6YR (Heme)
RN  - 81AH48963U (Molybdenum)
RN  - EC 1.8.3.1 (Sulfite Oxidase)
SB  - IM
MH  - Electrons
MH  - Heme/chemistry
MH  - Molybdenum/chemistry
MH  - Protein Domains
MH  - *Sulfite Oxidase
MH  - Sulfites
PMC - PMC8908248
OTO - NOTNLM
OT  - dimerization
OT  - electron transfer
OT  - enzyme kinetics
OT  - enzyme mechanism
OT  - heme
OT  - metalloenzyme
OT  - molybdenum
OT  - pre-steady-state kinetics
OT  - sulfite oxidase
COIS- Conflict of interest The authors declare that they have no conflicts of interest 
      with the contents of this article.
EDAT- 2022/02/06 06:00
MHDA- 2022/04/16 06:00
PMCR- 2022/02/02
CRDT- 2022/02/05 05:37
PHST- 2021/09/08 00:00 [received]
PHST- 2022/01/26 00:00 [revised]
PHST- 2022/01/28 00:00 [accepted]
PHST- 2022/02/06 06:00 [pubmed]
PHST- 2022/04/16 06:00 [medline]
PHST- 2022/02/05 05:37 [entrez]
PHST- 2022/02/02 00:00 [pmc-release]
AID - S0021-9258(22)00108-9 [pii]
AID - 101668 [pii]
AID - 10.1016/j.jbc.2022.101668 [doi]
PST - ppublish
SO  - J Biol Chem. 2022 Mar;298(3):101668. doi: 10.1016/j.jbc.2022.101668. Epub 2022 
      Feb 2.