[XK-related protein 4, processed form]: Phospholipid scramblase that promotes phosphatidylserine exposure on apoptotic cell surface (PubMed:25231987, PubMed:33725486, PubMed:37696806). Phosphatidylserine is a specific marker only present at the surface of apoptotic cells and acts as a specific signal for engulfment (PubMed:25231987, PubMed:37696806). {ECO:0000269|PubMed:25231987, ECO:0000269|PubMed:33725486, ECO:0000269|PubMed:37696806}. This is the function of Ensembl gene identifier ENSG00000206579 (XKR4, XK related 4).