An allosteric circuit in caspase-1

J Mol Biol. 2008 Sep 19;381(5):1157-67. doi: 10.1016/j.jmb.2008.06.040. Epub 2008 Jun 20.


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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Allosteric Regulation
  • Amino Acid Substitution
  • Arginine
  • Caspase 1 / chemistry
  • Caspase 1 / metabolism*
  • Conserved Sequence
  • Crystallography, X-Ray
  • DNA Mutational Analysis
  • Glutamic Acid
  • Humans
  • Hydrogen Bonding
  • Kinetics
  • Models, Molecular
  • Mutant Proteins / chemistry
  • Mutant Proteins / metabolism
  • Protein Structure, Secondary


  • Mutant Proteins
  • Glutamic Acid
  • Arginine
  • Caspase 1

Associated data

  • PDB/2H4W
  • PDB/2H4Y
  • PDB/2H51
  • PDB/2H54