Structure and function of Bacillus subtilis YphP, a prokaryotic disulfide isomerase with a CXC catalytic motif

Biochemistry. 2009 Sep 15;48(36):8664-71. doi: 10.1021/bi900437z.


The DUF1094 family contains over 100 bacterial proteins, all containing a conserved CXC motif, with unknown function. We solved the crystal structure of the Bacillus subtilis representative, the product of the yphP gene. The protein shows remarkable structural similarity to thioredoxins, with a canonical alphabetaalphabetaalphabetabetaalpha topology, despite low amino acid sequence identity to thioredoxin. The CXC motif is found in the loop immediately downstream of the first beta-strand, in a location equivalent to the CXXC motif of thioredoxins, with the first Cys occupying a position equivalent to the first Cys in canonical thioredoxin. The experimentally determined reduction potential of YphP is E degrees' = -130 mV, significantly higher than that of thioredoxin and consistent with disulfide isomerase activity. Functional assays confirmed that the protein displays a level of isomerase activity that might be biologically significant. We propose a mechanism by which the members of this family catalyze isomerization using the CXC catalytic site.

Publication types

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

MeSH terms

  • Amino Acid Motifs / genetics
  • Amino Acid Motifs / physiology
  • Amino Acid Sequence
  • Bacillus subtilis / enzymology*
  • Bacillus subtilis / genetics
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / physiology*
  • Catalysis
  • Catalytic Domain / genetics
  • Catalytic Domain / physiology*
  • Conserved Sequence / genetics
  • Crystallography, X-Ray
  • Cysteine / chemistry
  • Cysteine / genetics
  • Isomerism
  • Molecular Sequence Data
  • Multigene Family
  • Mutagenesis, Site-Directed
  • Protein Disulfide-Isomerases / chemistry*
  • Protein Disulfide-Isomerases / genetics
  • Protein Disulfide-Isomerases / physiology*
  • Sequence Alignment
  • Thioredoxins / chemistry
  • Thioredoxins / metabolism
  • Thioredoxins / physiology


  • Bacterial Proteins
  • Thioredoxins
  • Protein Disulfide-Isomerases
  • Cysteine

Associated data

  • PDB/3FHK