title: 4-A projection map of bacteriophage T4 DNA helix-destabilizing protein (gp32*I) crystal by 400-kV electron cryomicroscopy.
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.
authors.affiliation: Verna and Marrs and McLean Department of Biochemistry, Baylor College of Medicine, Houston, Texas 77030.
authors.forename: T
authors.initials: T
authors.lastname: Soejima
authors.forename: M B
authors.initials: MB
authors.lastname: Sherman
authors.forename: M F
authors.initials: MF
authors.lastname: Schmid
authors.forename: W
authors.initials: W
authors.lastname: Chiu
mesh_terms: D017122:Bacteriophage T4 / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D005615:Freezing; D008854:Microscopy, Electron; D011487:Protein Conformation; D012984:Software
chemical_list: D004268:DNA-Binding Proteins