Photorhabdus is a genus of gram-negative bioluminescent bacteria living in a symbiosis with Heterorhabditis nematodes forming a highly entomopathogenic complex. Such a complex is used in agriculture as a nature-based insecticide. However, some members of this genus are human pathogens as well. Understanding the mechanisms that determine interaction between Photorhabdus and its symbionts/hosts could be highly beneficial not only in biotechnologies but also in clinical reasearch and drug development.
Cell-cell interactions are frequently mediated by sugar-binding proteins – lectins. Based on the genome analysis, there has been identified potential lectins in number of Photorhabdus species. Recently, we examind two of them in further details, namely PLL from P. laumondii (formerly P. luminescens) [1] and PHL from P. asymbiotica [2,3]. Both lectins share the basic structural features, e.g. β-barrel fold with seven blades or presence of multiple binding sites per monomer. However, despite rather high sequence similarity, some non-marginal differences were detected: oligomeric state, binding site preferences and organization. This lead us to investigate this lectin family in further details.
We analyzed several homologues of proteins PLL and PHL from Photorhabdus spp. We managed to prepare some of them in recombinant form and perform basic analysis, as well as solve structure of these proteins in free form and in complexes with naturally occuring saccharide ligands. This research may not only reveal the differences in similar proteins from one family, but also answer the question, why single species of bacteria possess the ability to produce several similar lectins.
This work was supported by the Czech Science Foundation (project 13-25401S) and by the MEYS of the Czech Republic under the project CEITEC 2020 (LQ1601). CIISB research infrastructure project LM2015043 funded by MEYS CR is also gratefully acknowledged for the financial support of the measurements at the CF Biomolecular Interactions and Crystallization, CF X-ray Diffraction and Bio-SAXS and CF Proteomics at CEITEC (Brno, Czech Republic). We wish to thank the BESSY II (Berlin-Adlershof, Germany) and PETRA III (Hamburg, Germany) for access to their synchrotron data collection facilities and allocation of synchrotron radiation beam time.