| Popis: |
Plant diseases account for at least $220 billion of crop losses worldwide every year, and have a significant impact on global food security and bio-fuel availability. Bacterial, oomycetes and fungi pathogens secrete protein effectors into plant cells, where they perturb cellular processes, presumably to the benefit of the pathogen. In oomycetes, an N-terminal protein motif (RXLR) is important for targeting plant pathogen effectors into host cells (Whisson et al. 2007, Nature450, 115 and Oliva et al. 2010, Cell. Microbiol.12, 1015). However, little is known about the molecular mechanisms by which RXLR effectors manipulate host cell pathways. We have been studying the RXLR effector AVR3a11 (from Phytophthora capsici, a pathogen of pepper), which shares sequence similarity with the well-studied AVR3a effector from the Irish potato famine pathogen Phytophthora infestans (the causative agent of late blight in potato and tomato). Using a combination of 2D and 3D nuclear magnetic resonance (NMR) spectroscopy experiments, 75% of the AVR3a11 backbone has been assigned. With additional 13C-HSQC-NOESY and 15N-HSQC-NOESY experiments, a structural ensemble model has been generated which is in good agreement with the X-ray structure of AVR3a11 (PDB code 3ZR8, Boutemy et al. 2011, J. Biol. Chem.286, 35834). Backbone amide T1, T2 and heteronuclear NOE relaxation experiments at 800 MHz, show that AVR3a11 behaves as expected for a well ordered protein. However, the measured transverse relaxation is faster than theoretically expected for a protein this size, suggesting that conformational exchange may be occurring. Additional information on conformational exchange was obtained from hydrogen/deuterium exchange experiments. |
