title: A new apo-caspase-6 crystal form reveals the active conformation of the apoenzyme.
abstract: Caspase-6 has been identified as a key component in the pathway of neurodegenerative diseases such as Alzheimer's disease and Huntington's disease. It has been the focus of drug development for some time, but only recently have structural data become available. The first study identified a novel noncanonical conformation of apo-caspase-6 contrasting with the typical caspase conformation. Then, the structures of both caspase-6 zymogen and the Ac-VEID-CHO peptide inhibitor complex described caspase-6 in the canonical conformation, raising the question of why the intermediate between these two structures (mature apo-caspase-6) would adopt the noncanonical conformation. In this study, we present a new crystal form of the apoenzyme in the canonical conformation by identifying the previous apostructure as a pH-inactivated form of caspase-6. Our new apostructure is further compared to the Ac-VEID-CHO caspase-6 inhibitor complex. The structural comparison allows us to visualize the organization of loops L2, L3, and L4 upon ligand binding and how the catalytic groove forms to accommodate the inhibitor.
authors.affiliation: BioFocus, Chesterford Research Park, Saffron Walden, Essex CB10 1XL, UK.
authors.forename: Ilka
authors.initials: I
authors.lastname: Müller
authors.forename: Marieke B A C
authors.initials: MB
authors.lastname: Lamers
authors.forename: Alison J
authors.initials: AJ
authors.lastname: Ritchie
authors.forename: Hyunsun
authors.initials: H
authors.lastname: Park
authors.forename: Celia
authors.initials: C
authors.lastname: Dominguez
authors.forename: Ignacio
authors.initials: I
authors.lastname: Munoz-Sanjuan
authors.forename: Michel
authors.initials: M
authors.lastname: Maillard
authors.forename: Alex
authors.initials: A
authors.lastname: Kiselyov
mesh_terms: D001051:Apoenzymes / Q000737:chemistry / Q000378:metabolism; D053178:Caspase 6 / Q000737:chemistry* / Q000378:metabolism; D061945:Caspase Inhibitors; D020134:Catalytic Domain; D003460:Crystallization; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008024:Ligands; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D001051:Apoenzymes; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D008024:Ligands; D053178:Caspase 6