STRUCTURAL STUDIES OF NK RECEPTORS AND
LIGANDS
Tereza Skálová,1 Kristýna Kotýnková, 2,3 Jarmila Dušková, 1 Jindřich Hašek, 1 Andrea
Štěpánková, 1 Tomáš Kovaľ, 4 Petr Man, 2,3 Pavel Hanč, 2,3 Ondřej Vaněk, 2,3 Karel Bezouška, 2,3
and Jan Dohnálek 1
1Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Heyrovského nám. 2, 16206 Praha 6, Czech Republic,
2Department of Biochemistry, Faculty of Science, Charles University Prague, Hlavova 8, 12840 Praha 2, Czech Republic,
3Institute of Microbiology v.v.i., Academy of Sciences of Czech Republic, Vídeňská 1083, 14220 Praha 4, Czech Republic,
4Institute of Physics AS CR, v.v.i.,
Na Slovance 2, 182 21 Praha 8, Czech Republic,
t.skalova@gmail.com
Natural killer cells (NK cells) belong to lymphocytes, besides more familiar B and T-lymphocytes. They were discovered in 1970s [1]. 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 Clr-g [2], a target of this structural study, is a part of immune system of mouse. It is a ligand of NK receptor NKR-P1F. Clr-g occurs in dendritic cells and macrophages. The extracellular part of Clr-g was expressed, purified and crystallized. Structure was solved at 1.95 Å resolution using X-ray diffraction data measured at Bessy II of the Helmholtz Zentrum Berlin.
The overall
fold of mouse Clr-g is the fold typical of C-type lectin like proteins. Mouse Clr-g
forms dimers and is most similar to human CD69 [3].
An
interesting crystal contact was found in the crystal structure: N-terminus of
the extracellular part of Clr-g
binds to neighbour dimer in the crystal, and thus
shows feasibility of peptide binding into the central pocket of the dimer.
Mutual
orientation of monomers in the dimer is slightly
different than in the CD69 structure. However, moderate variability in
orientations of monomers was found also among single structures of CD69. It
seems that this difference gives testimony about flexibility in dimer formation and not about differences between mouse Clr-g and human CD69.
Electrostatic
potential was computed for several proteins structurally and functionally
related to mouse Clr-g and surprisingly big
differences were found.
1. R. Kiessling, E. Klein, H. Wigzell, Eur. J. Immunology, 5(2), (1975), 112-117.
2. B. Plougastel, C. Dubbelde, W. M. Yokoyama, Immunogenetics, 53, (2001), 209-214.
3. P. Kolenko, T. Skalova, O. Vanek, A. Stepankova, J. Duskova, J. Hasek, K. Bezouska, J. Dohnalek, Acta Crystallogr. F65, (2009), 1258-1260.
The authors wish to thank Uwe Müller for support at the
beam line BL14.1 of Bessy II,