Structure determination of a 16.8 kDa copper protein at 2.1 A resolution using anomalous scattering data with direct methods

Acta Crystallogr D Biol Crystallogr. 1998 Jul 1;54(Pt 4):629-35. doi: 10.1107/s0907444998005423.


The structure of rusticyanin, an acid-stable copper protein, has been determined at 2.1 A resolution by direct methods combined with the single-wavelength anomalous scattering (SAS) of copper (f" = 3.9 e-) and then conventionally refined (Rcryst = 18.7%, Rfree = 21.9%). This is the largest unknown protein structure (Mr approximately /= 16.8 kDa) to be determined using the SAS and direct-methods approach and demonstrates that by exploiting the anomalous signal at a single wavelength, direct methods can be used to determine phases at typical (approximately 2 A) macromolecular crystallographic resolutions. Extrapolating from the size of the anomalous signal for copper (f" approximately 4 e-), this result suggests that the approach could be used for proteins with molecular weights of up to 33 kDa per Se (f"max++ = 8 e- at the 'white line') and 80 kDa for a Pt derivative (f"max = 19 e- at the 'white line', L3 edge). The method provides a powerful alternative in solving a de novo protein structure without either preparing multiple crystals (i.e. isomorphous heavy-atom derivative plus native crystals) or collecting multi-wavelength anomalous diffraction (MAD) data.

MeSH terms

  • Azurin / analogs & derivatives*
  • Azurin / chemistry
  • Bacterial Proteins / chemistry*
  • Crystallography, X-Ray
  • Models, Molecular
  • Protein Conformation*
  • Thiobacillus / chemistry


  • Bacterial Proteins
  • rusticyanin
  • Azurin

Associated data

  • PDB/1A8Z