title: Structural and biochemical studies on procaspase-8: new insights on initiator caspase activation.
abstract: Caspases are proteases with an active-site cysteine and aspartate specificity in their substrates. They are involved in apoptotic cell death and inflammation, and dysfunction of these enzymes is directly linked to a variety of diseases. Caspase-8 initiates an apoptotic pathway triggered by external stimuli. It was previously characterized in its active inhibitor bound state by crystallography. Here we present the solution structure of the monomeric unprocessed catalytic domain of the caspase-8 zymogen, procaspase-8, showing for the first time the position of the linker and flexibility of the active site forming loops. Biophysical studies of carefully designed mutants allowed disentangling dimerization and processing, and we could demonstrate lack of activity of monomeric uncleaved procaspase-8 and of a processed but dimerization-incompetent mutant. The data provide experimental support in so-far unprecedented detail, and reveal why caspase-8 (and most likely other initiator caspases) needs the dimerization platform during activation.
authors.affiliation: Institute of Biochemistry, University of Zurich, CH-8057 Zurich, Switzerland.
authors.forename: Nadine
authors.initials: N
authors.lastname: Keller
authors.forename: Jirí
authors.initials: J
authors.lastname: Mares
authors.forename: Oliver
authors.initials: O
authors.lastname: Zerbe
authors.forename: Markus G
authors.initials: MG
authors.lastname: Grütter
mesh_terms: D000595:Amino Acid Sequence; D053181:Caspase 8 / Q000737:chemistry* / Q000378:metabolism; D020169:Caspases / Q000737:chemistry / Q000378:metabolism; D002384:Catalysis; D019281:Dimerization; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D013379:Substrate Specificity
chemical_list: D004792:Enzyme Precursors; D053181:Caspase 8; D020169:Caspases