Abstract
Sleeping sickness is a fatal disease caused by the protozoan parasite Trypanosoma brucei (Tb). Inosine-5’-monophosphate dehydrogenase (IMPDH) has been proposed as a potential drug target, since it maintains the balance between guanylate deoxynucleotide and ribonucleotide levels that is pivotal for the parasite. Here we report the structure of TbIMPDH at room temperature utilizing free-electron laser radiation on crystals grown in living insect cells. The 2.80 Å resolution structure reveals the presence of ATP and GMP at the canonical sites of the Bateman domains, the latter in a so far unknown coordination mode. Consistent with previously reported IMPDH complexes harboring guanosine nucleotides at the second canonical site, TbIMPDH forms a compact oligomer structure, supporting a nucleotide-controlled conformational switch that allosterically modulates the catalytic activity. The oligomeric TbIMPDH structure we present here reveals the potential of in cellulo crystallization to identify genuine allosteric co-factors from a natural reservoir of specific compounds.
Highlights
Sleeping sickness is a fatal disease caused by the protozoan parasite Trypanosoma brucei (Tb)
Depending on the size of the crystals, both synchrotron and X-ray free-electron lasers (XFELs) radiation has nowadays been used several-fold to elucidate structural information from recombinant proteins that form intracellular microcrystals, e.g., the coral fluorescent protein Xpa[12], the metazoan-specific kinase PAK413, and the BinAB larvicide from Lysinibacillus sphaericus[14]. It is still not clear if the phenomenon of in cellulo crystallization is restricted to a limited number of proteins that are evolutionary optimized for native crystal formation, or if living cells can be systematically exploited as crystal factories for a large number of recombinant proteins, when the associated cellular processes have been fully understood
The so far unknown GMP coordination mode observed in this study provides the molecular basis for a compact TbIMPDH octamer conformation that was previously associated with the inactive state of eukaryotic Inosine-5’-monophosphate dehydrogenase (IMPDH) by Buey et al.[28]
Summary
Sleeping sickness is a fatal disease caused by the protozoan parasite Trypanosoma brucei (Tb). Depending on the size of the crystals, both synchrotron and XFEL radiation has nowadays been used several-fold to elucidate structural information from recombinant proteins that form intracellular microcrystals, e.g., the coral fluorescent protein Xpa[12], the metazoan-specific kinase PAK413, and the BinAB larvicide from Lysinibacillus sphaericus[14] It is still not clear if the phenomenon of in cellulo crystallization is restricted to a limited number of proteins that are evolutionary optimized for native crystal formation, or if living cells can be systematically exploited as crystal factories for a large number of recombinant proteins, when the associated cellular processes have been fully understood. Due to the crucial role in de novo nucleotide biosynthesis and the significant clinical relevance, IMPDHs from various species are in the focus of investigations[18,19]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
