title: Crystal structure of the effector protein XOO4466 from Xanthomonas oryzae.
abstract: Many Gram-negative bacteria deliver their virulence factors into host cells through a secretion system. Those factors, called effector proteins, are involved in the pathogenicity in host cells by interfering with various cellular events. The phytopathogen Xanthomonas oryzae pv. oryzae uses a type III secretion system to inject its effectors, but the functional roles of these proteins remain largely uncharacterized. Here, we determined a crystal structure of XOO4466, an effector from X. oryzae pv. oryzae, and performed a functional analysis. We determined that XOO4466 is similar in sequence to Xanthomonas outer protein Q, a putative nucleoside hydrolase (NH). The overall structure of XOO4466 is homologous to that of NHs, including a metal-binding site, but differs in its oligomeric state and active site topology. Further analysis indicated that antiparallel β-strands commonly found in NHs adjacent to the active site loop are replaced in XOO4466 with a short loop, causing the active site loop to adopt a conformation distinct from that of NHs. Thus, the catalytic residues emanating from the respective active site loop of NHs are absent in the putative active site of XOO4466. Consistent with these structural features, a functional assay indicated that XOO4466 does not exhibit NH activity and possibly catalyzes yet unknown reactions.
authors.affiliation: Department of Agricultural Biotechnology, Seoul National University, Seoul, Republic of Korea.
authors.forename: Sangheon
authors.initials: S
authors.lastname: Yu
authors.forename: Ingyu
authors.initials: I
authors.lastname: Hwang
authors.forename: Sangkee
authors.initials: S
authors.lastname: Rhee
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009699:N-Glycosyl Hydrolases / Q000737:chemistry*; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D012459:Salicylates / Q000737:chemistry; D014974:Xanthomonas / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D012459:Salicylates; C027011:3,5-dinitrosalicylic acid; D009699:N-Glycosyl Hydrolases; D002118:Calcium
keywords: 3,5-dinitrosalicylic acid.; CU-NH; DNS; DTT; Effector protein; IAG-NH; IG-NH; IU-NH; NH; Nucleoside hydrolase; PCR; PEG; Pathogenicity; T3SS; TEV; Type III secretion system; Xanthomonas outer protein; Xanthomonas outer protein Q; Xop; cytidine and uridine-specific nucleoside hydrolase; dithiothreitol; inosine and guanosine-specific nucleoside hydrolase; inosine and uridine-specific nucleoside hydrolase; inosine, adenosine, and guanosine-specific nucleoside hydrolase; nucleoside hydrolase; polyethylene glycol; polymerase chain reaction; tobacco etch virus; type III secretion system