3Department of Biochemistry, Faculty of Science, Masaryk University, Kamenice 753/5, Brno 625 00, Czech Republic
Lectins are ubiquitous proteins and glycoproteins with the ability to specifically, non-covalently and reversibly bind to the mono-, oligo- and polysaccharides [1]. These sugar-binding proteins can be found in most organisms, ranging from viruses and bacteria to plants and animals. They play an important role in many processes occurring in nature such as cell-cell interaction or recognition of the host by a pathogen [2]. Lectins represent a heterogeneous group of proteins that vary in size, oligomeric state, structure as well as in exhibit specificity. Due to their importance, lectins are studied structurally and functionally to completely understand their role and mechanism of action [3].
Our research focuses on the lectins from gram-negative
entomopathogenic bacteria Photorhabdus asymbiotica, which live in symbiosis
with Heterorhabditis nematodes. This symbiotic complex can be found in
soil, where it searches for the insect prey [4]. Even though the Photorhabdus genus
is mainly insect pathogen there are also clinical cases describing a human
infection caused by this bacterium [5]. P. asymbiotica produces the
well-characterized lectin PHL [6] which has a seven-bladed β-propeller
fold and contains two types of binding sites for different ligands. In addition,
bioinformatic analysis of the P. asymbiotica genome revealed a
presence of two additional genes for homologous proteins with the PHL lectin.
Several sugar-binding proteins with unknown function and dual behaviour
makes
P. asymbiotica a compelling organism and further studies of biomolecules
produced by this bacterium may reveal their importance in the pathogenic or a
symbiotic stage of life.
Selected recombinant lectins were produced in the E. coli expression system and purified by affinity chromatography on a mannose-agarose resin. High-throughput crystallization screening was performed to find crystallization conditions using the sitting drop vapour diffusion method. Data collection from obtained crystals was performed on the synchrotron BESSYII. The structure of the PHL2 lectin was solved by molecular replacement using the PHL structure as a model.
This work has been supported by the Czech Science foundation (18-18964S).
[1] N. Sharon, H. Lis, Lectins, 2. ed, Springer, Dordrecht, 2007.
[2] J.F. Kennedy, P.M.G. Palva, M.T.S. Corella, M.S.M. Cavalcanti, L.C.B.B. Coelho, Lectins, versatile proteins of recognition: a review, Carbohydrate Polymers. 26 (1995) 219–230..
[3] H. Lis, N. Sharon, Lectins: Carbohydrate-Specific Proteins That Mediate Cellular Recognition, Chem. Rev. 98 (1998) 637–674.
[4] S. Forst, B. Dowds, N. Boemare, E. Stackebrandt, XENORHABDUS AND PHOTORHABDUS SPP.:Bugs That Kill Bugs, Annual Review of Microbiology. 51 (1997) 47–72.
[5] A. Hapeshi, N.R. Waterfield, Photorhabdus asymbiotica as an Insect and Human Pathogen, in: R.H. ffrench-Constant (Ed.), The Molecular Biology of Photorhabdus Bacteria, Springer International Publishing, Cham, 2017: pp. 159–177.
[6] G. Jančaříková, J. Houser, P. Dobeš, G. Demo, P. Hyršl, M. Wimmerová, Characterization of novel bangle lectin from Photorhabdus asymbiotica with dual sugar-binding specificity and its effect on host immunity, PLOS Pathogens. 13 (2017) e1006564.