Crystal structure determination of the fungal defense protein CCTX2

Fungi hold a vast repository of compounds and proteins that represent a valuable, but relatively unexplored, resource for both the pharmaceutical and biotechnological industry. Fungi often form expanded filamentous network in order to support their saprotrophic life style that relies on secretion of enzymes to decay surrounding organic matter. They are therefore often targeted by other soil dwelling organisms, such as nematodes. This has let to a molecular arms race and development of protein-based self-defense mechanisms. A new class of fungal self-defense proteins is represented by CCTX2 produced by Coprinopsis cinerea, which confers toxicity to the nematode Caenorhabditis elegans (Plaza et al. 2015 G3 6:87-98) Initial characterization suggests that CCTX2 is a chimerolectin, which also carries poly ADP-ribose polymerase (PARP) activity. Such domains have been found in bacterial toxins, but also in human regulatory proteins where they represent an important target in cancer treatment. Centrally to elucidating the molecular function of CCTX2 is the determination of the three dimensional structure of the protein, which is currently unknown.