STRUCTURE OF MOUSE CLRG – A LIGAND OF NK CELL RECEPTOR
T. Skálová,1 K. Kotýnková,2 J. Dušková,1 J. Hašek,1 A. Štěpánková,1 O. Vaněk,2,3 K. Bezouška,2,3 and J. Dohnálek 1
Institute of Macromolecular Chemistry,
2 Institute of Microbiology, v.v.i., Academy of Sciences of the Czech Republic, Vídeňská 1083, 14220 Prague 4, Czech Republic,
3 Department of Biochemistry, Faculty of Science, Charles University in Prague, Hlavova 8, 12840 Prague 2, Czech Republic,
Natural killer cells (NK cells) belong to lymphocytes, besides more familiar B and T-lymphocytes. They were discovered in 1970s . They comprise 5-10% of lymphocytes in blood and their role in the immune system is to discover and kill cells with cancer and cells infected by viruses. NK cells have a number of receptors on their surface, which are used for contact with other cells and for initiation of the cytotoxic response.
Protein Clrg , a target of this structural study, is a part of immune system of mouse. It is a ligand of NK receptor NKRP1F. Clrg occurs in dendritic cells and macrophages.
The extracellular part of Clrg was expressed, purified and crystallized. Diffraction data were collected at the synchrotron radiation source Bessy II of the Helmholtz Zentrum Berlin, beamline PX14.1 at temperature 100 K using a MAR Mosaic 225 CCD detector. Data were processed by HKL2000 with resolution 1.95 Å in space group P21212 and with unit-cell parameters 118.3, 61.4 and 32.4 Å. Molecular replacement was solved by BALBES in P2 using structure of the human CD69 . The solution was translated to a higher space group after the structure-building phase. The structure was refined in REFMAC to final R-factor 18.5 % and R-free 26.8 %.
The overall fold of mouse Clrg is very similar to that of human CD69. There are interesting crystal contacts which may indicate inter-molecular interactions between NK receptors and their ligands.
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The authors wish to thank Uwe Müller
for support at the beam line BL14.1 of Bessy II,