The invention provides a method of identifying an effective compound that modulates the binding of Humanin to Bax or Bid. The invention also provides a method of identifying an effective compound that modulates an activity of Bax or Bid. In addition, the invention provides a method of identifying a Humanin-like compound that binds to Bax or Bid or modulates an activity of Bax or Bid, or inhibits the apoptotic activity of Bax or Bid. The invention further provides an isolated polypeptide containing a mitochondrial-derived form of Humanin (SEQ ID NO:3) or a functional fragment thereof where the fragment contains the methionine at position 16 of SEQ ID NO:3.