Analysis of the minimal specificity of CED-3 using a yeast transcriptional reporter system.

Determination of the substrate specificity of site-specific proteases helps define their physiological roles. We developed a yeast-based system for defining the minimal substrate specificity of site-specific proteases, within the context of a protein. Using this system, we characterized the P4-P1 substrate specificity of the nematode apoptotic caspase CED-3. Apart from an absolute requirement for aspartate at the P1 position, CED-3 is a relatively promiscuous caspase capable of cleaving substrates bearing many amino acids at P4-P2 sites.