title: A case study on the treatment of protein SIRAS data.
abstract: A case study has been made on the treatment of the SIRAS (single isomorphous replacement with anomalous scattering) data of the originally unknown protein LegC3N. An alternative treatment has been proposed which led to improved results in this particular test case. The treatment involves iterative direct-method SAD (single-wavelength anomalous diffraction) phasing and direct-method-aided model completion, both of which are implanted in the IPCAS (Iterative Protein Crystal-structure Automatic Solution) pipeline. Apart from the experimental data, a simulated SIRAS data set for LegC3N with the derivative data truncated to 5.0 Å resolution has also been tested. SAD phasing and phase/model extension in PHENIX without direct methods failed to solve the structure using these simulated SIRAS data. However, the procedure proposed here involving direct methods in both SAD phasing and phase/model extension led to a nearly complete structure model. This shows the potential ability of treating SIRAS data with a derivative diffracting to lower resolution.
authors.affiliation: Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, People's Republic of China.
authors.forename: Deqiang
authors.initials: D
authors.lastname: Yao
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics and Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
authors.forename: Tao
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics and Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
authors.forename: Yao
authors.initials: Y
authors.lastname: He
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics and Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
authors.forename: Pu
authors.initials: P
authors.lastname: Han
authors.affiliation: Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
authors.forename: Maia
authors.initials: M
authors.lastname: Cherney
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics and Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
authors.forename: Yuanxin
authors.initials: Y
authors.lastname: Gu
authors.affiliation: Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
authors.forename: Miroslaw
authors.initials: M
authors.lastname: Cygler
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics and Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
authors.forename: Haifu
authors.initials: H
authors.lastname: Fan
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry; D018360:Crystallography, X-Ray / Q000379:methods*; D008958:Models, Molecular; D011506:Proteins / Q000737:chemistry*; D012984:Software
chemical_list: D001426:Bacterial Proteins; D011506:Proteins
keywords: SIRAS; direct-method SAD phasing; direct-method-aided model completion; proteins