Required for proper post-translational import and stabilization of peroxisomal membrane proteins (PMPs). Acts as a cytosolic import receptor for PMPs and delivers them to the docking factor PEX3 at the peroxisomal membrane for subsequent insertion into the membrane. Acts as a chaperone in stabilizing or maintaining PMPs in the lipid bilayer. Directs PEX17, a peripheral component of the peroxisomal matrix protein translocation machinery, to peroxisomes. Stabilizes VPS1, a protein required for peroxisomal fission, at the peroxisomal membrane. Also acts in conjunction with PEX3 in the formation of peroxisomes from preperoxisomal compartments at the endoplasmic reticulum during de novo peroxisome synthesis, probably via the import of additional PMPs. Interacts (farnesylated) with PEX3; farnesylation is required for this interaction. Interacts with PEX2, PEX5, PEX10, PEX11, PEX12, PEX13, PEX14, PEX17, PEX22, PEX25, PEX30 and PEX32; the interaction requires well-defined PEX19-binding sites within the peroxisomal membrane protein targeting signal (mPTS) of the PMPs and is independent on the presence of PEX3. Interacts with VPS1. Predominantly cytoplasmic (PubMed:9418908). Concentrates in a PEX3-dependent manner to defined foci on the endoplasmic reticulum membrane, which then bud off to form newly sythesized peroxisomes (PubMed:16009135). By oleic acid (at protein level). Present with 5350 molecules/cell in log phase SD medium. Belongs to the peroxin-19 family.