Tough Spots
This dataset was recorded from a crystal of CagL, a protein from Helicobacter pylori. Data from these crystals diffracted to approximately 2.8 Å resolution and could be solved by MR with a search model of the protein from a different crystal form. The appear to be of the Laue group 6/mmm, and can be processed in P6522 with a reasonable Rpim of 0.041 and 99% completeness. Phaser found an MR solution for one molecule per ASU in P6522 with a TFZ of 10.0. However, the Rfactor and Rfree values were stuck at approximately 0.36 and 0.44, respectively, despite no obvious errors or omissions in the electron density. Comments from a CCP4bb thread titled "Wrong Space Group?" (12/13/2013) supported the possibility of twinning, as evidenced by MR in lower symmetry space groups finding multiple molecule copies that could be refined to lower Rfactor and Rfree values. So the ultimate question is: What is the real space group?
Useful Information
Data kindly provided by: Dan Bonsor and Prof. Eric J. Sundberg, Institute of Human Virology, Department of Medicine and Department of Microbiology and Immunology, University of Maryland School of Medicine
Sample: CagL
Beamline where data were collected:
Wavelength: 0.979464 Å
Detector:
Oscillation angle: 0.4°
Exposure: 4 sec
Distance: 450 mm
Image file format: bzipped .img files
Protein sequence in FASTA format
Two options to download the data:
- Option 1 (easiest):
Use 'rsync' (linux/UNIX command) to download the compressed image files (command is in between quotes and should only be one line). There are 450 files of approximately 4.7 MB each:
and you will be prompted to enter 'lysozyme'.
- Option 2:
Use Wget to download the 'E1-2_2_#####.img.bz2' images (try this if you have a Windows OS).
