Binds phospholipid vesicles containing phosphatidylinositol 3-phosphate and participates in early endosomal trafficking. Interacts with BMX. May interact with SSB (By similarity). Interacts with RAB4 and RAB5 that have been activated by GTP-binding. Broadly expressed. The FYVE-type zinc finger domain mediates interactions with phosphatidylinositol 3-phosphate in membranes of early endosomes and penetrates bilayers. The FYVE domain insertion into PtdIns(3)P-enriched membranes is substantially increased in acidic conditions (By similarity). Phosphorylation on Tyr-393 and/or Tyr-404 is required for interaction with BMX and endosomal targeting.