The chaperone-like proteins RTP1S (the short isoform of RTP1) and RTP2 bind olfactory receptor (OR) proteins in the endoplasmic reticulum membrane (inferred from mouse homologs). In the absence of RTPs, most ORs are inefficiently translocated to the plasma membrane and accumulate in the Golgi and endoplasmic reticulum (inferred from mouse homologs). Some ORs are , however, translocated efficiently. Efficiently translocated ORs are called overrepresented ORs; inefficiently translocated ORs are called underrepresented ORs (inferred from mouse homologs). RTP2 inhibits translocation of some ORs (inferred from mouse homologs). The mechanism by which RTP1S and RTP2 facilitate translocation of ORs to the plasma membrane is not yet known.