2H54: Crystal Structure Of Human Caspase-1 (Thr388->ala) In Complex With 3- [2-(2-Benzyloxycarbonylamino-3-Methyl-Butyrylamino)-Propionylamino]- 4-Oxo-Pentanoic Acid (Z-Vad-Fmk)

Structural studies of caspase-1 reveal that the dimeric thiol protease can exist in two states: in an on-state, when the active site is occupied, or in an off-state, when the active site is empty or when the enzyme is bound by a synthetic allosteric ligand at the dimer interface approximately 15 A from the active site. A network of 21 hydrogen bonds from nine side chains connecting the active and allosteric sites change partners when going between the on-state and the off-state. Alanine-scanning mutagenesis of these nine side chains shows that only two of them-Arg286 and Glu390, which form a salt bridge-have major effects, causing 100- to 200-fold reductions in catalytic efficiency (k(cat)/K(m)). Two neighbors, Ser332 and Ser339, have minor effects, causing 4- to 7-fold reductions. A more detailed mutational analysis reveals that the enzyme is especially sensitive to substitutions of the salt bridge: even a homologous R286K substitution causes a 150-fold reduction in k(cat)/K(m). X-ray crystal structures of these variants suggest the importance of both the salt bridge interaction and the coordination of solvent water molecules near the allosteric binding pocket. Thus, only a small subset of side chains from the larger hydrogen bonding network is critical for activity. These form a contiguous set of interactions that run from one active site through the allosteric site at the dimer interface and onto the second active site. This subset constitutes a functional allosteric circuit or "hot wire" that promotes site-to-site coupling.
PDB ID: 2H54Download
MMDB ID: 99991
PDB Deposition Date: 2006/5/25
Updated in MMDB: 2012/05
Experimental Method:
x-ray diffraction
Resolution: 1.8  Å
Source Organism:
synthetic construct
Similar Structures:
Biological Unit for 2H54: hexameric; determined by author and by software (PISA,PQS)
Molecular Components in 2H54
Label Count Molecule
Proteins (6 molecules)
Caspase-1(Gene symbol: CASP1)
Molecule annotation
Caspase-1(Gene symbol: CASP1)
Molecule annotation
N-[(benzyloxy)carbonyl]-l-valyl-n-[(2s)-1-carboxy-4-fluoro- 3-oxobutan-2-yl]-l-alaninamide
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB