3CSL

HasA/R (PDB id 3CSL) is a complex of a 22-stranded beta-barrel outer membrane protein (HAsR, 865 residues), its hemophore (HasA, 206 residues), and heme. The structure and its biological implications are described in "Heme uptake across the outer membrane as revealed by crystal structures of the receptor-hemophore complex" (Krieg, S., Huché, F., Diederichs, K., Izadi-Pruneyre, N., Lecroisey, A., Wandersman, C., Delepelaire, P., Welte, W. (2009), Proc. Nat. Acad. Sci. Vol. 106 pp. 1045-1050.)

3-wl SeMet-MAD data were collected at beamline X06SA of the SLS in November 2006 on a MarCCD detector. HasA/R crystallizes in spacegroup F222; cell parameters are a=157Å, b=163Å, c=596Å. There are 2 complexes per ASU. Data to about 3.0Å could be collected from this crystal, but the anomalous data are useful to about 5Å only. The ordered part of HasR has residues 112-865 and harbours 9 SeMet residues. The ordered part of HasA has 173 residues, one of which is SeMet - but that is mostly disordered.

These MAD data, giving a structure with an average B of 100 Å2, constitute a project that is challenging for humans, and currently too difficult for automatic methods of structure solution and model building. The deposited 3CSL structure was not obtained from these MAD data alone, but the model was actually refined against slightly better (2.7Å) data collected on a native crystal at the ESRF.

XDS data reduction of high-remote, peak and inflection

The script generate_XDS.INP may be used to get a suitable first XDS.INP file for each of the three wavelengths. Unfortunately the beamline software did not put the correct X and Y position of the direct beam into the header. So you will have to find this yourself, using adxv or XDS-viewer. Or just use:

ORGX= 1536 ORGY= 1520 

The other thing that you might want to try yourself, or just fill in, is

VALUE_RANGE_FOR_TRUSTED_DETECTOR_PIXELS=8000. 30000. ! often 8000 is ok

instead of the the default (7000. 30000.). This gives a good mask for the beamstop shadow.

Other than that, the three MAD wavelengths can be processed once with default parameters, as written into XDS.INP by generate_XDS.INP. This data reduction therefore proceeds in spacegroup P1. After that,

mv GXPAM.XDS XPARM.XDS

and another (optimized) integration pass should be performed, after setting

JOBS= INTEGRATE CORRECT

This second pass proceeds in the correct spacegroup (22) which was identified by CORRECT at the end of the first pass.

High-remote

Due to a beamline problem, high-remote data collection stopped after 269 frames of 0.5° (the final frame is already affected). After restart of the beamline, another 100 frames were collected but they later turned out to merge badly with the first 269 frames - a hint that the monochromator was still heating up, or similar. So the latter frames were left out. The 269 frames are here (1.4 Gb).

Peak

360 frames (0.5° oscillation) at the peak wavelength were collected after the high-remote data. They can be downloaded from here (1.9 Gb).

Inflection

360 frames (0.5° oscillation) at the inflection wavelength were collected after the peak data. They can be downloaded from here (1.8 Gb).