Title : Structures of glycosylated mammalian glutaminyl cyclases reveal conformational variability near the active center
Abstract :
- Formation of N-terminal pyroglutamate (pGlu or pE) from glutaminyl or glutamyl precursors is catalyzed by glutaminyl cyclases (QC)
- As the formation of pGlu-amyloid has been linked with Alzheimer's disease, inhibitors of QCs are currently the subject of intense development
- Here, we report three crystal structures of N-glycosylated mammalian QC from humans (hQC) and mice (mQC)
- Whereas the overall structures of the enzymes are similar to those reported previously, two surface loops in the neighborhood of the active center exhibit conformational variability
- Furthermore, two conserved cysteine residues form a disulfide bond at the base of the active center that was not present in previous reports of hQC structure
- Site-directed mutagenesis suggests a structure-stabilizing role of the disulfide bond
- At the entrance to the active center, the conserved tryptophan residue, W(207) , which displayed multiple orientations in previous structure, shows a single conformation in both glycosylated human and murine QCs
- Although mutagenesis of W(207) into leucine or glutamine altered substrate conversion significantly, the binding constants of inhibitors such as the highly potent PQ50 (PBD150) were minimally affected
- The crystal structure of PQ50 bound to the active center of murine QC reveals principal binding determinants provided by the catalytic zinc ion and a hydrophobic funnel
- This study presents a first comparison of two mammalian QCs containing typical, conserved post-translational modifications