6hv6
Crystal structure of PatoxP, a cysteine protease-like domain of Photorhabdus asymbiotica toxin PaTox
Structural highlights
FunctionPATOX_PHOAA Toxin that acts on host cells by modifying Rho proteins by tyrosine GlcNAcylation and heterotrimeric G alpha proteins by deamidation. Catalyzes the mono-O-GlcNAcylation of small GTPases of the Rho family (RhoA, RhoB, RhoC, Rac1, Rac2, Rac3, Cdc42) in eukaryotic host cells at the conserved tyrosine residue located in the switch I region (Tyr-32/34), using UDP-N-acetylglucosamine (UDP-GlcNAc) as the sugar donor; other GTPases of the Rho, Ras or Rab families are not substrates. Tyrosine glycosylation inhibits Rho activation and prevents interaction with downstream effectors, resulting in actin disassembly, inhibition of phagocytosis, cell rounding, and toxicity toward insects and mammalian cells. Also catalyzes the deamidation of the catalytic glutamine in heterotrimeric G alpha proteins (Gi, Gq/11), which blocks GTP hydrolysis and arrests the G proteins in a permanent active state leading to activation of Rho GTPases. Thus, PaTox hijacks host GTPase signaling in a bidirectional manner by deamidation-induced activation and glycosylation-induced inactivation of GTPases.[1] Publication Abstract from PubMedThe nematode mutualistic bacterium Photorhabdus asymbiotica produces a large virulence-associated multifunctional protein toxin named PaTox. A glycosyltransferase domain and a deamidase domain of this large toxin function as effectors that specifically target host Rho GTPases and heterotrimeric G proteins, respectively. Modification of these intracellular regulators results in toxicity toward insects and mammalian cells. In this study, we identified a cysteine protease-like domain spanning PaTox residues 1844-2114 (PaTox(P)), upstream of these two effector domains and characterized by three conserved amino acid residues (Cys-1865, His-1955, and Asp-1975). We determined the crystal structure of the PaTox(P) C1865A variant by native single-wavelength anomalous diffraction of sulfur atoms (sulfur-SAD). At 2.0 A resolution, this structure revealed a catalytic site typical for papain-like cysteine proteases, comprising a catalytic triad, oxyanion hole, and typical secondary structural elements. The PaTox(P) structure had highest similarity to that of the AvrPphB protease from Pseudomonas syringae classified as a C58-protease. Furthermore, we observed that PaTox(P) shares structural homology also with non-C58-cysteine proteases, deubiquitinases, and deamidases. Upon delivery into insect larvae, PaTox(P) alone without full-length PaTox had no toxic effects. Yet, PaTox(P) expression in mammalian cells was toxic and enhanced the apoptotic phenotype induced by PaTox in HeLa cells. We propose that PaTox(P) is a C58-like cysteine protease module that is essential for full PaTox activity. A cysteine protease-like domain enhances the cytotoxic effects of the Photorhabdus asymbiotica toxin PaTox.,Bogdanovic X, Schneider S, Levanova N, Wirth C, Trillhaase C, Steinemann M, Hunte C, Aktories K, Jank T J Biol Chem. 2018 Nov 26. pii: RA118.005043. doi: 10.1074/jbc.RA118.005043. PMID:30478175[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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