May act as a substrate-specific adapter of an E3 ubiquitin-protein ligase complex (CUL3-RBX1-BTB) which mediates the ubiquitination and subsequent proteasomal degradation of target proteins (By similarity). Involved in leaf vasculature patterning (PubMed:18643975). Protein modification; protein ubiquitination. Expressed in emerging leaf primordia. The BTB/POZ domain mediates the interaction with some component of ubiquitin ligase complexes. Defects in shoot and primary root growth and aberrant parallel venation pattern in juvenile leaves. Belongs to the NPH3 family.