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Publikationen - Molekulare Signalverarbeitung

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Publikation

Kopycki, J.; Wieduwild, E.; Kohlschmidt, J.; Brandt, W.; Stepanova, A.N.; Alonso, J.M.; Pedras, M.S.; Abel, S.; Grubb, C.D. Kinetic analysis of Arabidopsis glucosyltransferase UGT74B1 illustrates a general mechanism by which enzymes can escape product inhibition Biochem J 450, 37-46, (2013) DOI: 10.1042/BJ20121403

Plant genomes encode numerous small molecule glycosyltransferases which modulate the solubility, activity, immunogenicity and/or reactivity of hormones, xenobiotics and natural products. The products of these enzymes can accumulate to very high concentrations, yet somehow avoid inhibiting their own biosynthesis. Glucosyltransferase UGT74B1 (UDP-glycosyltransferase 74B1) catalyses the penultimate step in the core biosynthetic pathway of glucosinolates, a group of natural products with important functions in plant defence against pests and pathogens. We found that mutation of the highly conserved Ser284 to leucine [wei9-1 (weak ethylene insensitive)] caused only very mild morphological and metabolic phenotypes, in dramatic contrast with knockout mutants, indicating that steady state glucosinolate levels are actively regulated even in unchallenged plants. Analysis of the effects of the mutation via a structural modelling approach indicated that the affected serine interacts directly with UDP-glucose, but also predicted alterations in acceptor substrate affinity and the kcat value, sparking an interest in the kinetic behaviour of the wild-type enzyme. Initial velocity and inhibition studies revealed that UGT74B1 is not inhibited by its glycoside product. Together with the effects of the missense mutation, these findings are most consistent with a partial rapid equilibrium ordered mechanism. This model explains the lack of product inhibition observed both in vitro and in vivo, illustrating a general mechanism whereby enzymes can continue to function even at very high product/precursor ratios.
Publikation

Feussner, I.; Wasternack, C. Lipoxygenase catalyzed oxygenation of lipids Fett/Lipid 100, 146-152, (1998)

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Publikation

Hertel, S.; Knöfel, H.-D.; Kramell, R.; Miersch, O. Partial purification and characterization of a jasmonic acid conjugate cleaving amidohydrolase from the fungus <EM>Botryodiplodia theobromae</EM> FEBS Letters 407, 105-110, (1997)

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Publikation

Görschen, E.; Dunaeva, M.; Reeh, I.; Wasternack, C. Overexpression of the jasmonate inducible 23 kDa protein (JIP 23) from barley in transgenic tobacco leads to the repression of leaf proteins FEBS Letters 419, 58-62, (1997)

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Publikation

Feussner, K.; Feussner, I.; Leopold, I.; Wasternack, C. Isolation of a cDNA coding for an ubiquitin-conjugating enzyme UBCI of tomato - the first stress-induced UBC of higher plants FEBS Letters 409, 211-215, (1997)

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Publikation

Feussner, I.; Kühn, H.; Wasternack, C. Hypothesis. Do specific linoleate 13-lipoxygenases initiate b-oxidation? FEBS Letters 406, 1-5, (1997)

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Publikation

Bohlmann, H.; Vignutelli, A.; Hilpert, B.; Miersch, O.; Wasternack, C.; Apel, K. Wounding and chemicals induce expression of the Arabidopsis gene Thi2.1, encoding a fungal defense thionin, via the octadecanoid pathway FEBS Letters 437, 281-286, (1998)

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Publikation

Morgan, K.E.; Zarembinski, T.I.; Theologis, A.; Abel, S. Biochemical characterization of recombinant polypeptides corresponding to the predicted ßαα-fold in Aux/IAA proteins FEBS Letters 454, 283-287, (1999)

The plant hormone indoleacetic acid (IAA or auxin) transcriptionally activates a select set of early genes. The Auxl IAA class of early auxin-responsive genes encodes a large family of short-lived, nuclear proteins. Aux/IAA polypeptides homo-and heterodimerize, and interact with auxin-response transcription factors (ARFs) via C-terminal regions conserved in both protein families. This shared region contains a predicted βαα motif similar to the prokaryotic β-Ribbon DNA binding domain, which mediates both protein dimerization and DNA recognition. Here, we show by circular dichroism spectroscopy and by chemical cross-linking experiments that recombinant peptides corresponding to the predicted βαα region of three Aux/IAA proteins from Arabidopsis thaliana contain substantial α-helical secondary structure and undergo homo- and heterotypic interactions in vitro. Our results indicate a similar biochemical function of the plant βαα domain and suggest that the βαα fold plays an important role in mediating combinatorial interactions of Aux/IAA and ARF proteins to specifically regulate secondary gene expression in response to auxin.
Publikation

Schilling, S.; Stenzel, I.; von Bohlen, A.; Wermann, M.; Schulz, K.; Demuth, H.-U.; Wasternack, C. Isolation and characterization of the glutaminyl cyclases from Solanum tuberosum and Arabidopsis thaliana: implications for physiological functions Biol. Chem 388, 145-153, (2007) DOI: 10.1515/BC.2007.016

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Publikation

Guranowski, A.; Miersch, O.; Staswick, P.E.; Suza, W.; Wasternack, C. Substrate specificity and products of side-reactions catalyzed by jasmonate:amino acid synthetase (JAR1) FEBS Letters 581, 815-820, (2007) DOI: 10.1016/j.febslet.2007.01.049

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