VHL (von Hippel-Lindau disease tumor suppressor) is the substrate recognition subunit for an E3 ligase activity that ubiquitinates proteins containing hydroxyproline residues.  Targets of VHL include HIF1 alpha, beta 2 adrenergic receptor, ZHX2 and others.  In VHL-box E3 Ubiquitin ligases, VHL is bound to a heterodimer complex composed of Elongin B (ELOB) and Elongin C (ELOC) through the "BC-box motif" found in many proteins in the VHL-box and SOCS-box protein families.  ELOB/ELOC serves as an adapter between substrate recognition proteins and Cullin-2 (or Cullin-5) and RBX1 to form an active E3 ligase.