title: Effects of crystal twinning on the ability to solve a macromolecular structure using multiwavelength anomalous diffraction.
abstract: The crystal structure of gpD, the capsid-stabilizing protein of bacteriophage lambda, was solved by multiwavelength anomalous diffraction (MAD) for a selenomethionine (SeMet) derivative of the protein at 1.8 A resolution, using crystals in space group P2(1) [Yang et al. (2000), Nature Struct. Biol. 7, 230-237]. Subsequent analysis showed that the crystals of both the original protein and the SeMet derivative were pseudo-merohedrally twinned with a twinning fraction approximately 0.36, owing to the near-identity of the a and c axes. An analysis of the crystal structure solution is presented and the utility of twinned crystals for solving the structure using MAD and of different phasing strategies is discussed; the results obtained with several software packages are compared.
authors.affiliation: Protein Structure Section, Macromolecular Crystallography Laboratory, Program in Structural Biology, National Cancer Institute-FCRDC, Frederick, MD 21702, USA.
authors.forename: F
authors.initials: F
authors.lastname: Yang
authors.forename: Z
authors.initials: Z
authors.lastname: Dauter
authors.forename: A
authors.initials: A
authors.lastname: Wlodawer
mesh_terms: D002213:Capsid / Q000737:chemistry*; D036022:Capsid Proteins; D003460:Crystallization; D018360:Crystallography, X-Ray / Q000379:methods; D006023:Glycoproteins / Q000737:chemistry*; D046911:Macromolecular Substances; D012645:Selenomethionine; D012984:Software; D055672:Static Electricity
chemical_list: D036022:Capsid Proteins; D006023:Glycoproteins; D046911:Macromolecular Substances; C406073:gpD protein, lambda phage; D012645:Selenomethionine