Crystal structure of pyrrolizidine alkaloid N-oxygenase from the grasshopper Zonocerus variegatus

The high-resolution crystal structure of the flavin-dependent monooxygenase (FMO) from the African locust Zonocerus variegatus is presented and the kinetics of structure-based protein variants are discussed. Z. variegatus expresses three flavin-dependent monooxygenase (ZvFMO) isoforms which contribute to a counterstrategy against pyrrolizidine alkaloids (PAs). PAs are protoxic compounds produced by some angiosperm lineages as a chemical defence against herbivores. N-Oxygenation of PAs and the accumulation of PA N-oxides within their haemolymph result in two evolutionary advantages for these insects: (i) they circumvent the defence mechanism of their food plants and (ii) they can use PA N-oxides to protect themselves against predators, which cannot cope with the toxic PAs. Despite a high degree of sequence identity and a similar substrate spectrum, the three ZvFMO isoforms differ greatly in enzyme activity. Here, the crystal structure of the Z. variegatus PA N-oxygenase (ZvPNO), the most active ZvFMO isoform, is reported at 1.6 Å resolution together with kinetic studies of a second isoform, ZvFMOa. This is the first available crystal structure of an FMO from class B (of six different FMO subclasses, A–F) within the family of flavin-dependent monooxygenases that originates from a more highly developed organism than yeast. Despite the differences in sequence between family members, their overall structure is very similar. This indicates the need for high conservation of the three-dimensional structure for this type of reaction throughout all kingdoms of life. Nevertheless, this structure provides the closest relative to the human enzyme that is currently available for modelling studies. Of note, the crystal structure of ZvPNO reveals a unique dimeric arrangement as well as small conformational changes within the active site that have not been observed before. A newly observed kink within helix α8 close to the substrate-binding path might indicate a potential mechanism for product release. The data show that even single amino-acid exchanges in the substrate-entry path, rather than the binding site, have a significant impact on the specific enzyme activity of the isoforms

Überbau : Relations of production in architecture in the Anthropocene

Gedruckt erschienen im Universitätsverlag der TU Berlin, ISBN 978-3-7983-3213-3Wo werden die Rohstoffe für die fortschrittverheißenden architektonischen und infrastrukturellen Großprojekte in Stahl und Beton abgebaut? Wie ist Architektur mit dem globalen System der Lieferketten verstrickt? Wer profitiert von der Verteilung von Grund und Boden? Welche Arbeits- bedingungen herrschen auf europäischen Großbaustellen? Und in bundesrepublikanischen Architekturbüros? Wie wird Architektur heute produziert? Die Publikation handelt von Umweltzerstörung und Land Grabbing der Zementindustrie in Indonesien und Vietnam, den Methoden der Sandmafia am Mekong, und die Extrakti- on von Lithium in Bolivien für die Batterien unserer Smart Cities. Sie beleuchtet strukturelle bodenpolitische Ungleich- heiten und die prekären Anstellungsverhältnisse jener Ar- chitekturmachender, die bei der Betrachtung spektakulärer Neubauten zumeist vergessen werden. So werden die For- men architektonischer Gouvernementalität greifbar.Where do the raw materials for the large-scale and process-promissing architectural and infrastructural projects in steel and concrete come from? How is architecture entangled with the global system of supply chains? Who benefits from the distribution of property? What are the working conditions on major European construction sites? And in German architectural offices? How is architecture produced today? The publication deals with environmental destruction and land grabbing by the cement industry in Indonesia and Vietnam, the methods of the sand mafia on the Mekong, and the extraction of lithium in Bolivia for the batteries of our smart cities. It sheds light on structural inequalities in land policy and the precarious employment conditions of those who make architecture, who are usually forgotten in the contemplation of spectacular new buildings. In this way, the forms of architectural governmentality become tangible