Ionic interactions near the loop L4 are important for maintaining the active-site environment and the dimer stability of (pro)caspase 3.

ABSTRACT: We have examined the role of a salt bridge between Lys242 and Glu246 in loop L4 of procaspase 3 and of mature caspase 3, and we show that the interactions are required for stabilizing the active site. Replacing either of the residues with an alanine residue results in a complete loss of procaspase 3 activity. Although both mutants are active in the context of the mature caspase 3, the mutations result in an increase in K(m) and a decrease in kcat when compared with the wild-type caspase 3. In addition, the mutations result in an increase in the pK(a) value associated with a change in kcat with pH, but does not affect the transition observed for Km versus pH. The mutations also affect the accessibility of the active-site solvent as measured by tryptophan fluorescence emission in the presenc

SUBMITTER: Feeney B 

PROVIDER: S-EPMC1134137 | biostudies-literature | 2004 Dec

REPOSITORIES: biostudies-literature