title: Extended substrate recognition in caspase-3 revealed by high resolution X-ray structure analysis.
abstract: Caspases are cysteine proteases involved in the signalling cascades of programmed cell death in which caspase-3 plays a central role, since it propagates death signals from intrinsic and extrinsic stimuli to downstream targets. The atomic resolution (1.06 Angstroms) crystal structure of the caspase-3 DEVD-cmk complex reveals the structural basis for substrate selectivity in the S4 pocket. A low-barrier hydrogen bond is observed between the side-chains of the P4 inhibitor aspartic acid and Asp179 of the N-terminal tail of the symmetry related p12 subunit. Site-directed mutagenesis of Asp179 confirmed the significance of this residue in substrate recognition. In the 1.06 Angstroms crystal structure, a radiation damage induced rearrangement of the inhibitor methylketone moiety was observed. The carbon atom that in a substrate would represent the scissile peptide bond carbonyl carbon clearly shows a tetrahedral coordination and resembles the postulated tetrahedral intermediate of the acylation reaction.
authors.affiliation: Biochemisches Institut, Universität Zürich, Switzerland.
authors.forename: Rajkumar
authors.initials: R
authors.lastname: Ganesan
authors.forename: Peer R E
authors.initials: PR
authors.lastname: Mittl
authors.forename: Stjepan
authors.initials: S
authors.lastname: Jelakovic
authors.forename: Markus G
authors.initials: MG
authors.lastname: Grütter
mesh_terms: D001665:Binding Sites / Q000235:genetics; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006801:Humans; D006860:Hydrogen Bonding; D007700:Kinetics; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000737:chemistry; D013379:Substrate Specificity
chemical_list: D061945:Caspase Inhibitors; D021122:Protein Subunits; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases