Structural and nucleotide-binding properties of YajQ and YnaF, two Escherichia coli proteins of unknown function

Protein Sci. 2002 Nov;11(11):2551-60. doi: 10.1110/ps.0217502.


Structural genomics is a new approach in functional assignment of proteins identified via whole-genome sequencing programs. Its rationale is that nonhomologous proteins performing similar or related biological functions might have similar tertiary structure. We used dye pseudoaffinity chromatography, two-dimensional gel electrophoresis, and mass spectrometry to identify two novel Escherichia coli nucleotide-binding proteins, YnaF and YajQ. YnaF exhibited significant sequence identity with MJ0577, an ATP-binding protein from a hyperthermophile (Methanococcus jannaschii), and with UspA, a protein from Haemophilus influenzae that belongs to the Universal Stress Protein family. YnaF conserves the ATP-binding site and the dimeric structure observed in the crystal of MJ0577. The protein YajQ, present in many bacterial genomes, is missing in eukaryotes. In the absence of significant similarities of YajQ to any solved structure, we determined its structural and ligand-binding properties by NMR and isothermal titration calorimetry. We demonstrate that YajQ is composed of two domains, each centered on a beta-sheet, that are connected by two helical segments. NMR studies, corroborated with local sequence conservation among YajQ homologs in various bacteria, indicate that one of the beta-sheets is mostly involved in biological activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Amino Acid Sequence
  • Calorimetry
  • Circular Dichroism
  • Dimerization
  • Escherichia coli Proteins / chemistry*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / isolation & purification
  • Escherichia coli Proteins / metabolism*
  • Ligands
  • Models, Molecular
  • Molecular Sequence Data
  • Molecular Structure
  • Nuclear Magnetic Resonance, Biomolecular
  • Nucleotides / metabolism
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Proteome
  • RNA-Binding Proteins / chemistry*
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / isolation & purification
  • RNA-Binding Proteins / metabolism*
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Sequence Alignment


  • Escherichia coli Proteins
  • Ligands
  • Nucleotides
  • Proteome
  • RNA-Binding Proteins
  • Recombinant Proteins
  • YajQ protein, E coli
  • YnaF protein, E coli
  • Adenosine Triphosphate