Comparison of phasing methods for sulfur-SAD using in-house chromium radiation: case studies for standard proteins and a 69 kDa protein
✍ Scribed by Watanabe, Nobuhisa ;Kitago, Yu ;Tanaka, Isao ;Wang, Jia-wei ;Gu, Yuan-xin ;Zheng, Chao-de ;Fan, Hai-fu
- Publisher
- International Union of Crystallography
- Year
- 2005
- Tongue
- English
- Weight
- 826 KB
- Volume
- 61
- Category
- Article
- ISSN
- 0907-4449
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✦ Synopsis
Phasing of the crystal structures of four standard proteins (lysozyme, trypsin, glucose isomerase and thaumatin) and a novel 69 kDa protein from Thermus thermophilus, TT0570, was performed using the single-wavelength anomalous diffraction of S atoms intrinsically present within the native protein molecules. To utilize the sulfur anomalous diffraction, the data sets were collected using the loopless data-collection method with chromium K X-rays of wavelength 2.29 A ˚. Three phasing methods, MLPHARE, SHARP and OASIS-2004, were tested in combination with the DM or SOLOMON density-modification method. The results showed that the solvent contents are still an important factor for phasing with the S-SAD method, even when longer wavelength Cr K radiation is used. Of the three procedures, the improved direct phasing of OASIS-2004 with its implemented fragment feedback to the direct-method probability calculation gave the best results in determining the initial phases. For all five proteins, almost the entire models could be built automatically.