New family of bacterial lectins with seven-bladed b-propeller fold

 

Petra Sýkorová1, Jitka Novotná2,3, Gabriel Demo2,3, Eva Dejmková2, Jan Komárek2,3,  Lucia Hároníková1, Annabelle Varrot4, Anne Imberty4, Martina Pokorná2,3 and Michaela Wimmerová 1,2,3

 

1 Department of Biochemistry, Faculty of Science, Masaryk University, Brno, Czech Republic 2National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno, Czech Republic

 3Central European Institute of Technology, Masaryk University, Brno, Czech Republic

 4CERMAV CNRS affiliated to Université de Grenoble, France

guliver@mail.muni.cz

 

Burkholderia pseudomallei and Chromobacterium violaceum are bacteria of tropical and subtropical soil and water that occasionally can cause fatal infections in human and animals [1-3]. Lectins of these bacteria, BP39L and CV39L, were discovered and characterized. Lectins are proteins, which are capable of specific and reversible binding to carbohydrate moieties. Carbohydrate-mediated recognition plays an important role in the ability of pathogenic bacteria to adhere to the surface of the host cell in the first step of their invasion and infectivity [4].

The crystal structures of BP39L and CV39L were determined based on a new class of lanthanide complexes for heavy atom derivatization (SAD experiment). The BP39L lectin crystallized in I222 space group (a = 46.08 Ǻ b = 87.55 Ǻ and c = 159.10 Ǻ) and CV39L in P212121 (a = 65.71 Ǻ b = 123.78 Ǻ and c = 180.93 Ǻ). The structures of both lectins revealed seven-bladed b-propeller fold with possibly seven binding sites per monomer. The BP39L lectin was observed as a monomer and CV39L as a dimer in solution, which was confirmed also in the crystal structure. The knowledge about the structure together with sequence and structure predictions indicates that the proteins belong to an undescribed new family of lectins. The binding sites of BP39L are highly conserved. On the other hand, CV39L has not equivalent binding sites but the architecture is very similar. In both lectin binding sites, highly conserved Trp residues were observed, which play a key role in saccharide stabilization via stacking and polar (hydrogen bond) interactions. Isothermal titration calorimetry experiments conducted on a series of saccharides confirmed the preference of BP39L for d-mannose and α-1,3(α-1,6)-d-mannotriose, and CV39L for l-fucose and l-galactose. As the architecture of the binding sites of both lectins has a shape of wider shallow pocket, it indicates that the lectins can recognize more complex saccharides as just monosaccharides. This structural feature was also indicated by the molecular docking simulations based on the orientation of the saccharide ring of d-mannose (BP39L), l-fucose and l-galactose (CV39L).

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2.       G.C. Whitlock, D.M. Estes and A.G. Torres. FEMS Microbiol. Lett. 27, (2007), 115-122.

3.       C.H. Yang and Y.H. Li. J. Chin. Med. Assoc. 74, (2011), 435-441.

4.       H. Lis and N. Sharon. Chem. Rev. 98, (1998), 637-674.

 

We thank the synchrotron facility PETRA-III (DESY, Hamburg, Germany) for access to their macromolecular beam line P13 and the allocation of synchrotron beam time. This work was supported by the Czech Science Foundation (P207/11/P185 and GA13-25401S).