title: Structures of human Golgi-resident glutaminyl cyclase and its complexes with inhibitors reveal a large loop movement upon inhibitor binding.
abstract: Aberrant pyroglutamate formation at the N terminus of certain peptides and proteins, catalyzed by glutaminyl cyclases (QCs), is linked to some pathological conditions, such as Alzheimer disease. Recently, a glutaminyl cyclase (QC) inhibitor, PBD150, was shown to be able to reduce the deposition of pyroglutamate-modified amyloid-β peptides in brain of transgenic mouse models of Alzheimer disease, leading to a significant improvement of learning and memory in those transgenic animals. Here, we report the 1.05-1.40 Å resolution structures, solved by the sulfur single-wavelength anomalous dispersion phasing method, of the Golgi-luminal catalytic domain of the recently identified Golgi-resident QC (gQC) and its complex with PBD150. We also describe the high-resolution structures of secretory QC (sQC)-PBD150 complex and two other gQC-inhibitor complexes. gQC structure has a scaffold similar to that of sQC but with a relatively wider and negatively charged active site, suggesting a distinct substrate specificity from sQC. Upon binding to PBD150, a large loop movement in gQC allows the inhibitor to be tightly held in its active site primarily by hydrophobic interactions. Further comparisons of the inhibitor-bound structures revealed distinct interactions of the inhibitors with gQC and sQC, which are consistent with the results from our inhibitor assays reported here. Because gQC and sQC may play different biological roles in vivo, the different inhibitor binding modes allow the design of specific inhibitors toward gQC and sQC.
authors.affiliation: Institute of Biological Chemistry, Core Facility for Protein Production and X-ray Structural Analysis, Academia Sinica, Taipei, Taiwan.
authors.forename: Kai-Fa
authors.initials: KF
authors.lastname: Huang
authors.forename: Su-Sen
authors.initials: SS
authors.lastname: Liaw
authors.forename: Wei-Lin
authors.initials: WL
authors.lastname: Huang
authors.forename: Cho-Yun
authors.initials: CY
authors.lastname: Chia
authors.forename: Yan-Chung
authors.initials: YC
authors.lastname: Lo
authors.forename: Yi-Ling
authors.initials: YL
authors.lastname: Chen
authors.forename: Andrew H-J
authors.initials: AH
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D019881:Aminoacyltransferases / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000494:pharmacology*; D006056:Golgi Apparatus / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid
chemical_list: D004791:Enzyme Inhibitors; D019881:Aminoacyltransferases; C059280:glutaminyl-peptide cyclotransferase