The structure of ligand-free glutaminyl cyclase (QC) from Drosophila melanogaster (DmQC) has been determined in a novel crystal form. The protein crystallized in space group I4, with unit-cell parameters a = b = 122.3, c = 72.7 Å. The crystal diffracted to a resolution of 2 Å at the home source. The structure was solved by molecular replacement and was refined to an R factor of 0.169. DmQC exhibits a typical α/β-hydrolase fold. The electron density of three monosaccharides could be localized. The accessibility of the active site will facilitate structural studies of novel inhibitor-binding modes.
Keywords: Drosophila melanogaster; glutaminyl cyclase; soaking.