Sakari Kauppinen

Pep-13, a plant defense-inducing pathogen-associated pattern from Phytophthora transglutaminases.

Innate immunity, an ancient form of defense against microbial infection, is well described for animals and is also suggested to be important for plants. Discrimination from self is achieved through receptors that recognize pathogen‐associated molecular patterns (PAMPs) not found in the host. PAMPs are evolutionarily conserved structures which are functionally important and, thus, not subject to frequent mutation. Here we report that the previously described peptide elicitor of defense responses in parsley, Pep‐13, constitutes a surface‐exposed fragment within a novel calcium‐dependent cell wall transglutaminase (TGase) from Phytophthora sojae. TGase transcripts and TGase activity are detectable in all Phytophthora species analyzed, among which are some of the most destructive plant pathogens. Mutational analysis within Pep‐13 identified the same amino acids indispensable for both TGase and defense‐eliciting activity. Pep‐13, conserved among Phytophthora TGases, activates defense in parsley and potato, suggesting its function as a genus‐specific recognition determinant for the activation of plant defense in host and non‐host plants. In summary, plants may recognize PAMPs with characteristics resembling those known to trigger innate immune responses in animals.

Short strong hydrogen bonds in proteins: a case study of rhamnogalacturonan acetylesterase

The short hydrogen bonds in rhamnogalacturonan acetylesterase have been investigated by structure determination of an active-site mutant, 1H NMR spectra and computational methods. Comparisons are made to database statistics. A very short carboxylic acid carboxylate hydrogen bond, buried in the protein, could explain the low-field (18 p.p.m.) 1H NMR signal.

A stepwise optimization of crystals of rhamnogalacturonan lyase from Aspergillus aculeatus

Recombinant rhamnogalacturonan lyase from Aspergillus aculeatus has been crystallized by a stepwise procedure and X-ray diffraction data have been collected. The crystals were grown using hanging-drop vapour-diffusion and microseeding techniques. Crystals were obtained showing a flat plate morphology. The crystallization conditions were 20% PEG 4000, 9% PEG 400, 0.1 M (NH(4))(2)SO(4) and 0.1 M sodium acetate pH 4.4. These crystals diffracted to a resolution of 1.5 A. The unit-cell parameters are a = b = 77.0, c = 170.8 A with the possible space group P4(3)2(1)2 or P4(1)2(1)2. There is most likely to be one molecule in the asymmetric unit, leading to a calculated solvent content of approximately 47% for the crystals.

Crystallization and preliminary X-ray studies of rhamnogalacturonase A from Aspergillus aculeatus

Recombinant rhamnogalacturonase A from Aspergillus aculeatus has been crystallized and X-ray diffraction data has been collected. Crystals were grown by the hanging-drop vapour-diffusion technique, under the conditions 10% PEG 8000, 0.05 M KH(2)PO(4) and 0.1 M sodium acetate buffered at pH 3.5. The crystals diffract beyond 2.0 A resolution and belong to one of the orthorhombic space groups I2(1)2(1)2(1) or I222, with the unit-cell parameters a = 62.9, b = 125.4 and c = 137.0 A. There is one molecule in the asymmetric unit and a solvent content of approximately 54%. The enzyme is highly glycosylated corresponding to 5.9 kDa.