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Publication Abstract from PubMed

Glutaminyl cyclases (QCs), which catalyze the formation of pyroglutamic acid (pGlu) at the N-terminus of a variety of peptides and proteins, have attracted particular attention for their potential role in Alzheimer's disease. In a transgenic Drosophila melanogaster (Dm) fruit fly model, oral application of the potent competitive QC inhibitor PBD150 was shown to reduce the burden of pGlu-modified Abeta. In contrast to mammals such as humans and rodents, there are at least three DmQC species, one of which (isoDromeQC) is localized to mitochondria, whereas DromeQC and an isoDromeQC splice variant possess signal peptides for secretion. Here we present the recombinant expression, characterization and crystal structure determination of mature DromeQC and isoDromeQC, revealing a similar overall fold to mammalian QCs. In the case of isoDromeQC, the putative extended substrate binding site might be affected by proximity of the N-terminal residues. PBD150 inhibition of DromeQC is roughly one order of magnitude lower than that of the human and murine QCs. The inhibitor binds to isoDromeQC in a similar fashion to that observed for human QCs, whereas it adopts alternative binding modes in a DromeQC variant lacking the conserved cysteines near to the active center and shows a disordered dimethoxyphenyl moiety in wild type DromeQC, providing an explanation for the lower affinity. Our biophysical and structural data suggest that isoDromeQC and human QC are similar with regard to functional aspects. The two Dm enzymes represent a suitable model for further in depth analysis of the catalytic mechanism of animal QCs, and isoDromeQC might serve as a model system for structure based design of potential AD therapeutics.

Crystal Structures of Glutaminyl Cyclases from Drosophila melanogaster Reveal Active Site Conservation between Insect and Mammalian QCs.,Koch B, Kolenko P, Buchholz M, Ruiz Carrillo D, Parthier C, Wermann M, Rahfeld JU, Reuter G, Schilling S, Stubbs MT, Demuth HU Biochemistry. 2012 Aug 16. PMID:22897232^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.