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The crystal structure of type III effector protein XopQ from Xanthomonas oryzae complexed with adenosine diphosphate ribose
Author(s) -
Yu Sangheon,
Hwang Ingyu,
Rhee Sangkee
Publication year - 2014
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.24656
Subject(s) - effector , ribose , active site , moiety , biochemistry , chemistry , nucleoside , binding site , hydrolase , ligand (biochemistry) , protein structure , stereochemistry , biology , enzyme , receptor
Effector proteins are virulence factors that promote pathogenesis by interfering with various cellular events and are delivered directly into host cells by the secretion systems of many Gram‐negative bacteria. Type III effector protein XOO4466 from the plant pathogen Xanthomonas oryzae pv. oryzae (XopQ Xoo ) and XopQ homologs from other phytopathogens have been predicted to be nucleoside hydrolases based on their sequence similarities. However, despite such similarities, recent structural and functional studies have revealed that XopQ Xoo does not exhibit the expected activity of a nucleoside hydrolase. On the basis of the conservation of a Ca 2+ coordination shell of a ribose‐binding site and the spacious active site in XopQ Xoo , we hypothesized that a novel compound containing a ribosyl moiety could serve as a substrate for XopQ Xoo . Here, we report the crystal structure of XopQ Xoo in complex with adenosine diphosphate ribose (ADPR), which is involved in regulating cytoplasmic Ca 2+ concentrations in eukaryotic cells. ADPR is bound to the active site of XopQ Xoo with its ribosyl end tethered to the Ca 2+ coordination shell. The binding of ADPR is further stabilized by interactions mediated by hydrophobic residues that undergo ligand‐induced conformational changes. These data showed that XopQ Xoo is capable of binding a novel chemical bearing a ribosyl moiety, thereby providing the first step toward understanding the functional role of XopQ Xoo . Proteins 2014; 82:2910–2914. © 2014 Wiley Periodicals, Inc.