4-A projection map of bacteriophage T4 DNA helix-destabilizing protein (gp32*I) crystal by 400-kV electron cryomicroscopy

J Struct Biol. 1993 Jul-Aug;111(1):9-16. doi: 10.1006/jsbi.1993.1030.

Abstract

Ice-embedded crystals of bacteriophage T4 DNA helix-destabilizing protein gp32*I were imaged by computer-controlled spot-scanning on a 400-kV electron cryomicroscope. gp32*I crystals generally have different steps of thickness within a crystal; each step can have different symmetry. Multivariate statistical analysis enabled us to unambiguously select spot-scan images that consist entirely of one motif which were processed subsequently by crystallographic Fourier-averaging techniques. The computed phases of the resulting reflections were evaluated for symmetry in projection, and some of those images were correlated with independent thickness measurements of freeze-dried samples of the same crystals. The structure factors with pgg symmetry from nine spot-scan images were merged, and the mean figure of merit of merged phases was better than 0.9 for data at resolution up to 4 A. A projection map was generated and showed multiple density peaks that corresponded to the high-resolution features of gp32*I.

Publication types

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

MeSH terms

  • Bacteriophage T4 / metabolism*
  • DNA-Binding Proteins / chemistry*
  • DNA-Binding Proteins / ultrastructure*
  • Freezing
  • Microscopy, Electron
  • Protein Conformation
  • Software

Substances

  • DNA-Binding Proteins