Protein that regulates peroxisome populations; interacts with Pex11p, Pex25p, and Pex27p to control both constitutive peroxisome division and peroxisome morphology and abundance during peroxisome proliferation; mediates contacts between mitochondria and peroxisomes that stimulate transport of citrate, converted from acetyl-CoA, from peroxisomes to mitochondria; peroxisomal integral membrane protein that is enriched at peroxisomal-mitochondrial (PerMit) contact sites