Evolution of a new class of prenyl transferases of secondary metabolism
LUTZ HEIDE
Pharmazeutisches Institut der Universität Tübingen
Auf der Morgenstelle 8
D-72076 Tübingen
heide@uni-tuebingen.de
http://www.uni-tuebingen.de/pharmazie/abteilungen/biologie/
Prenyltransferases which prenylate aromatic substrates have led to the evolution of an impressive variety of secondary metabolites in plants, fungi and bacteria. Our group discovered the first member of a new class of enzymes involved in the prenylation of aromatic compounds. A second member was discovered in 2005, and the X-ray structure of that protein was determined at the Salk Institute in the USA. These proteins show a completely novel protein fold, characterized by a barrel with antiparallel beta strands. They do not share sequence similarity with previously known proteins.
Within the work in EVOMET, we have now discovered two further members of this prenyltransferase family. Genetic and biochemical studies have been carried out to determine the biosynthetic function of these enzymes. During a recent sabbatical at the Salk Institute, USA, this applicant has overexpressed and purified both enzymes, and crystallized one of them (Ept2, see Figure). The X-ray structure was determined and showed strict conservation of the protein architecture in this enzyme class. The active site of the enzyme is localized in the center of the barrel, in a highly protected environment. This class of prenyltransferases yields soluble, stable biocatalysts of excellent biotechnological applicability. A special advantage of these enzymes, and a striking difference to the majority of previously known prenyltransferases, is the independence of several members of this group from magnesium ions or other divalent cations.
In cooperation with other groups of EVOMET, we now investigate the reaction mechanism of these enzymes and the biosynthetic routes to hemiterpenoid secondary metabolites. Identification of additional members of this class will be used to elucidated the evolutionary relationships between these proteins.
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