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Mou TC, Zeng B, Doukov TI, Sprang SR. Application of sulfur SAD to small crystals with a large asymmetric unit and anomalous substructure. Acta Crystallogr D Struct Biol 2022; 78:1021-1031. [PMID: 35916226 PMCID: PMC9344479 DOI: 10.1107/s2059798322005848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 05/31/2022] [Indexed: 11/17/2022] Open
Abstract
The application of sulfur single-wavelength anomalous dispersion (S-SAD) to determine the crystal structures of macromolecules can be challenging if the asymmetric unit is large, the crystals are small, the size of the anomalously scattering sulfur structure is large and the resolution at which the anomalous signals can be accurately measured is modest. Here, as a study of such a case, approaches to the SAD phasing of orthorhombic Ric-8A crystals are described. The structure of Ric-8A was published with only a brief description of the phasing process [Zeng et al. (2019), Structure, 27, 1137-1141]. Here, alternative approaches to determining the 40-atom sulfur substructure of the 103 kDa Ric-8A dimer that composes the asymmetric unit are explored. At the data-collection wavelength of 1.77 Å measured at the Frontier micro-focusing Macromolecular Crystallography (FMX) beamline at National Synchrotron Light Source II, the sulfur anomalous signal strength, |Δano|/σΔano (d''/sig), approaches 1.4 at 3.4 Å resolution. The highly redundant, 11 000 000-reflection data set measured from 18 crystals was segmented into isomorphous clusters using BLEND in the CCP4 program suite. Data sets within clusters or sets of clusters were scaled and merged using AIMLESS from CCP4 or, alternatively, the phenix.scale_and_merge tool from the Phenix suite. The latter proved to be the more effective in extracting anomalous signals. The HySS tool in Phenix, SHELXC/D and PRASA as implemented in the CRANK2 program suite were each employed to determine the sulfur substructure. All of these approaches were effective, although HySS, as a component of the phenix.autosol tool, required data from all crystals to find the positions of the sulfur atoms. Critical contributors in this case study to successful phase determination by SAD included (i) the high-flux FMX beamline, featuring helical-mode data collection and a helium-filled beam path, (ii) as recognized by many authors, a very highly redundant, multiple-crystal data set and (iii) the inclusion within that data set of data from crystals that were scanned over large ω ranges, yielding highly isomorphous and highly redundant intensity measurements.
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Affiliation(s)
- Tung Chung Mou
- Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT 59812, USA
| | - Baisen Zeng
- Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT 59812, USA
| | - Tzanko I Doukov
- Macromolecular Crystallography Group, Stanford Synchrotron Radiation Light Source, SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94309, USA
| | - Stephen R Sprang
- Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT 59812, USA
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Guimarães BG, Golinelli-Pimpaneau B. De novo crystal structure determination of double stranded RNA binding domain using only the sulfur anomalous diffraction in SAD phasing. Curr Res Struct Biol 2021; 3:112-120. [PMID: 34235491 PMCID: PMC8244422 DOI: 10.1016/j.crstbi.2021.05.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 05/07/2021] [Accepted: 05/31/2021] [Indexed: 10/25/2022] Open
Abstract
Single-wavelength anomalous dispersion (SAD)-phasing using sulfur as the unique anomalous scatterer is a powerful method to solve the phase problem in protein crystallography. However, it is not yet widely used by non-expert crystallographers. We report here the structure determination of the double stranded RNA binding domain of human dihydrouridine synthase using the sulfur-SAD method and highly redundant data collected at 1.8 Å ("off-edge"), at which the estimated overall anomalous signal was 1.08%. High multiplicity data were collected on a single crystal rotated along the ϕ or ω axis at different κ angles, with the primary beam intensity being attenuated from 50% to 95%, compared to data collection at 0.98 Å, to reduce radiation damage. SHELXD succeeded to locate 14 out 15 sulfur sites only using the data sets recorded with highest beam attenuation, which provided phases sufficient for structure solving. In an attempt to stimulate the use of sulfur-SAD phasing by a broader community of crystallographers, we describe our experimental strategy together with a compilation of previous successful cases, suggesting that sulfur-SAD phasing should be attempted for determining the de novo structure of any protein with average sulfur content diffracting better than 3 Å resolution.
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Affiliation(s)
| | - Béatrice Golinelli-Pimpaneau
- Laboratoire de Chimie des Processus Biologiques, UMR 8229 CNRS, Collège de France, Sorbonne Université, 11 Place Marcelin Berthelot, 75005 Paris, France
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Olczak A, Cianci M. The signal-to-noise ratio in SAD experiments. CRYSTALLOGR REV 2017. [DOI: 10.1080/0889311x.2017.1386182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Andrzej Olczak
- Institute of General and Ecological Chemistry, Lodz University of Technology, Lodz, Poland
| | - Michele Cianci
- Department of Agricultural, Food and Environmental Sciences, Università Politecnica delle Marche, Ancona, Italy
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Hegde RP, Fedorov AA, Sauder JM, Burley SK, Almo SC, Ramagopal UA. The hidden treasure in your data: phasing with unexpected weak anomalous scatterers from routine data sets. Acta Crystallogr F Struct Biol Commun 2017; 73:184-195. [PMID: 28368276 PMCID: PMC5379167 DOI: 10.1107/s2053230x17002680] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Accepted: 02/16/2017] [Indexed: 12/25/2022] Open
Abstract
Single-wavelength anomalous dispersion (SAD) utilizing anomalous signal from native S atoms, or other atoms with Z ≤ 20, generally requires highly redundant data collected using relatively long-wavelength X-rays. Here, the results from two proteins are presented where the anomalous signal from serendipitously acquired surface-bound Ca atoms with an anomalous data multiplicity of around 10 was utilized to drive de novo structure determination. In both cases, the Ca atoms were acquired from the crystallization solution, and the data-collection strategy was not optimized to exploit the anomalous signal from these scatterers. The X-ray data were collected at 0.98 Å wavelength in one case and at 1.74 Å in the other (the wavelength was optimized for sulfur, but the anomalous signal from calcium was exploited for structure solution). Similarly, using a test case, it is shown that data collected at ∼1.0 Å wavelength, where the f'' value for sulfur is 0.28 e, are sufficient for structure determination using intrinsic S atoms from a strongly diffracting crystal. Interestingly, it was also observed that SHELXD was capable of generating a substructure solution from high-exposure data with a completeness of 70% for low-resolution reflections extending to 3.5 Å resolution with relatively low anomalous multiplicity. Considering the fact that many crystallization conditions contain anomalous scatterers such as Cl, Ca, Mn etc., checking for the presence of fortuitous anomalous signal in data from well diffracting crystals could prove useful in either determining the structure de novo or in accurately assigning surface-bound atoms.
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Affiliation(s)
- Raghurama P. Hegde
- Division of Biological Sciences, Poornaprajna Institute of Scientific Research, #4, 16th Cross, Sadashivnagar, Bangalore 560 080, India
| | - Alexander A. Fedorov
- Department of Biochemistry, Albert Einstein College of Medicine, Ullmann Building, Jack and Pearl Resnick Campus, 1300 Morris Park Avenue, Bronx, New York, NY 10461, USA
| | - J. Michael Sauder
- Lilly Biotechnology Center, Eli Lilly and Company, 10290 Campus Point Drive, San Diego, CA 92121, USA
| | - Stephen K. Burley
- RCSB Protein Data Bank, Center for Integrative Proteomics Research, Rutgers University, The State University of New Jersey, 174 Frelinghuysen Road, Piscataway, NJ 08854, USA
- Institute of Quantitative Biomedicine, Rutgers University, The State University of New Jersey, Piscataway, NJ 08854, USA
- Rutgers Cancer Institute of New Jersey, Rutgers University, The State University of New Jersey, New Brunswick, NJ 08903, USA
- RCSB Protein Data Bank, San Diego Supercomputer Center, San Diego, California, USA
- Skaggs School of Pharmacy and Pharmceutical Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Steven C. Almo
- Department of Biochemistry, Albert Einstein College of Medicine, Ullmann Building, Jack and Pearl Resnick Campus, 1300 Morris Park Avenue, Bronx, New York, NY 10461, USA
| | - Udupi A. Ramagopal
- Division of Biological Sciences, Poornaprajna Institute of Scientific Research, #4, 16th Cross, Sadashivnagar, Bangalore 560 080, India
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Liebschner D, Yamada Y, Matsugaki N, Senda M, Senda T. On the influence of crystal size and wavelength on native SAD phasing. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY 2016; 72:728-41. [PMID: 27303793 DOI: 10.1107/s2059798316005349] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2015] [Accepted: 03/29/2016] [Indexed: 11/11/2022]
Abstract
Native SAD is an emerging phasing technique that uses the anomalous signal of native heavy atoms to obtain crystallographic phases. The method does not require specific sample preparation to add anomalous scatterers, as the light atoms contained in the native sample are used as marker atoms. The most abundant anomalous scatterer used for native SAD, which is present in almost all proteins, is sulfur. However, the absorption edge of sulfur is at low energy (2.472 keV = 5.016 Å), which makes it challenging to carry out native SAD phasing experiments as most synchrotron beamlines are optimized for shorter wavelength ranges where the anomalous signal of sulfur is weak; for longer wavelengths, which produce larger anomalous differences, the absorption of X-rays by the sample, solvent, loop and surrounding medium (e.g. air) increases tremendously. Therefore, a compromise has to be found between measuring strong anomalous signal and minimizing absorption. It was thus hypothesized that shorter wavelengths should be used for large crystals and longer wavelengths for small crystals, but no thorough experimental analyses have been reported to date. To study the influence of crystal size and wavelength, native SAD experiments were carried out at different wavelengths (1.9 and 2.7 Å with a helium cone; 3.0 and 3.3 Å with a helium chamber) using lysozyme and ferredoxin reductase crystals of various sizes. For the tested crystals, the results suggest that larger sample sizes do not have a detrimental effect on native SAD data and that long wavelengths give a clear advantage with small samples compared with short wavelengths. The resolution dependency of substructure determination was analyzed and showed that high-symmetry crystals with small unit cells require higher resolution for the successful placement of heavy atoms.
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Affiliation(s)
- Dorothee Liebschner
- Structural Biology Research Center, Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba 305-0801, Japan
| | - Yusuke Yamada
- Structural Biology Research Center, Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba 305-0801, Japan
| | - Naohiro Matsugaki
- Structural Biology Research Center, Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba 305-0801, Japan
| | - Miki Senda
- Structural Biology Research Center, Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba 305-0801, Japan
| | - Toshiya Senda
- Structural Biology Research Center, Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba 305-0801, Japan
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