For each of the following proteins that are proteolytically cleaved in apoptosis, indicate whether the cleavage is first carried out by an initiator (I) or executioner (E) caspase. Your answer would be a five-letter string composed of letters I and E only, e.g. EEEII.
( ) The initiator caspase-2
( ) The executioner caspase-3
( ) The BH3-only protein Bid
( ) The endonuclease inhibitor iCAD
( ) The nuclear protein Lamin A

Question

For each of the following proteins that are proteolytically cleaved in apoptosis, indicate whether the cleavage is first carried out by an initiator (I) or executioner (E) caspase. Your answer would be a five-letter string composed of letters I and E only, e.g. EEEII.
( )	The initiator caspase-2
( )	The executioner caspase-3
( )	The BH3-only protein Bid
( )	The endonuclease inhibitor iCAD
( )	The nuclear protein Lamin A

Quizplus · Accepted Answer

Initiator caspases are cleaved and activated when brought into proximity. They then cleave and activate their downstream executioner caspases and initiate caspase cascades. Whereas very few other substrates, including Bid, are also cleaved by initiator caspases, the great majority of over a thousand identified caspase substrates are thought to be cleaved by executioner caspases to orchestrate apoptosis.

For Each of the Following Proteins That Are Proteolytically Cleaved