A Single DNA Point Mutation Leads to the Formation of a Cysteine-Tyrosine Crosslink in the Cysteine Dioxygenase from Bacillus subtilis

Biochemistry. 2023 Jun 20;62(12):1964-1975. doi: 10.1021/acs.biochem.3c00083. Epub 2023 Jun 7.

Abstract

Cysteine dioxygenase (CDO) is a non-heme iron-containing enzyme that catalyzes the oxidation of cysteine (Cys) to cysteine sulfinic acid (CSA). Crystal structures of eukaryotic CDOs revealed the presence of an unusual crosslink between the sulfur of a cysteine residue (C93 in Mus musculus CDO, MmCDO) and a carbon atom adjacent to the phenyl group of a tyrosine residue (Y157). Formation of this crosslink occurs over time as a byproduct of catalysis and increases the catalytic efficiency of CDO by at least 10-fold. Interestingly, in bacterial CDOs, the residue corresponding to C93 is replaced by a highly conserved glycine (G82 in Bacillus subtilis CDO, BsCDO), which precludes the formation of a C-Y crosslink in these enzymes; yet bacterial CDOs achieve turnover rates paralleling those of fully crosslinked eukaryotic CDOs. In the present study, we prepared the G82C variant of BsCDO to determine if a single DNA point mutation could lead to C-Y crosslink formation in this enzyme. We used gel electrophoresis, peptide mass spectrometry, electron paramagnetic resonance spectroscopy, and kinetic assays to characterize this variant alongside the natively crosslinked wild-type (WT) MmCDO and the natively non-crosslinked WT BsCDO. Collectively, our results provide compelling evidence that the G82C BsCDO variant is indeed capable of C-Y crosslink formation. Our kinetic studies indicate that G82C BsCDO has a reduced catalytic efficiency compared to WT BsCDO and that activity increases as the ratio of crosslinked to non-crosslinked enzyme increases. Finally, by carrying out a bioinformatic analysis of the CDO family, we were able to identify a large number of putatively crosslinked bacterial CDOs, the majority of which are from Gram-negative pathogenic bacteria.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacillus subtilis* / genetics
  • Bacillus subtilis* / metabolism
  • Cysteine Dioxygenase* / chemistry
  • Cysteine Dioxygenase* / genetics
  • Cysteine* / genetics
  • Kinetics
  • Mice
  • Point Mutation
  • Tyrosine / genetics

Substances

  • Cysteine
  • Cysteine Dioxygenase
  • Tyrosine