title: Structural and phylogenetic analyses of the GP42 transglutaminase from Phytophthora sojae reveal an evolutionary relationship between oomycetes and marine Vibrio bacteria.
abstract: Transglutaminases (TGases) are ubiquitous enzymes that catalyze selective cross-linking between protein-bound glutamine and lysine residues; the resulting isopeptide bond confers high resistance to proteolysis. Phytophthora sojae, a pathogen of soybean, secretes a Ca(2+)-dependent TGase (GP42) that is activating defense responses in both host and non-host plants. A GP42 fragment of 13 amino acids, termed Pep-13, was shown to be absolutely indispensable for both TGase and elicitor activity. GP42 does not share significant primary sequence similarity with known TGases from mammals or bacteria. This suggests that GP42 has evolved novel structural and catalytic features to support enzymatic activity. We have solved the crystal structure of the catalytically inactive point mutant GP42 (C290S) at 2.95 Å resolution and identified residues involved in catalysis by mutational analysis. The protein comprises three domains that assemble into an elongated structure. Although GP42 has no structural homolog, its core region displays significant similarity to the catalytic core of the Mac-1 cysteine protease from Group A Streptococcus, a member of the papain-like superfamily of cysteine proteases. Proteins that are taxonomically related to GP42 are only present in plant pathogenic oomycetes belonging to the order of the Peronosporales (e.g. Phytophthora, Hyaloperonospora, and Pythium spp.) and in marine Vibrio bacteria. This suggests that a lateral gene transfer event may have occurred between bacteria and oomycetes. Our results offer a basis to design and use highly specific inhibitors of the GP42-like TGase family that may impair the growth of important oomycete and bacterial pathogens.
authors: Interfakultäres Institut für Biochemie, Universität Tübingen, 72076 Tübingen, Germany.
authors: Kerstin
authors: K
authors: Reiss
authors: Interfakultäres Institut für Biochemie, Universität Tübingen, 72076 Tübingen, Germany.
authors: Eva
authors: E
authors: Kirchner
authors: Agri-Food Canada, London, Ontario N5V 4T3, Canada.
authors: Mark
authors: M
authors: Gijzen
authors: Interfakultäres Institut für Biochemie, Universität Tübingen, 72076 Tübingen, Germany.
authors: Georg
authors: G
authors: Zocher
authors: Zentrum für Molekularbiologie der Pflanzen, Universität Tübingen, 72076 Tübingen, Germany.
authors: Birgit
authors: B
authors: Löffelhardt
authors: Zentrum für Molekularbiologie der Pflanzen, Universität Tübingen, 72076 Tübingen, Germany.
authors: Thorsten
authors: T
authors: Nürnberger
authors: Interfakultäres Institut für Biochemie, Universität Tübingen, 72076 Tübingen, Germany; Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232. Electronic address: thilo.stehle@uni-tuebingen.de.
authors: Thilo
authors: T
authors: Stehle
authors: Zentrum für Molekularbiologie der Pflanzen, Universität Tübingen, 72076 Tübingen, Germany. Electronic address: frederic.brunner@zmbp.uni-tuebingen.de.
authors: Frédéric
authors: F
authors: Brunner
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D018360:Crystallography, X-Ray / Q000379:methods; D004252:DNA Mutational Analysis; D019143:Evolution, Molecular; D007113:Immunity, Innate; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009868:Oomycetes / Q000378:metabolism*; D028528:Petroselinum / Q000382:microbiology; D010802:Phylogeny; D010838:Phytophthora / Q000235:genetics*; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D011198:Solanum tuberosum / Q000382:microbiology; D011503:Transglutaminases / Q000378:metabolism; D014733:Vibrio / Q000378:metabolism*; D014871:Water Microbiology
chemical_list: D011994:Recombinant Proteins; D011503:Transglutaminases