<Tr> <Th_colspan="2"> Other data </Th> </Tr> <Tr> <Th> Locus </Th> <Td> Chr. 6 p21. 3 </Td> </Tr> <P> Transporter associated with antigen processing (TAP) is a member of the ATP - binding - cassette transporter family . It delivers cytosolic peptides into the endoplasmic reticulum (ER), where they bind to nascent MHC class I molecules . </P> <P> The TAP structure is formed of two proteins: TAP - 1 and TAP - 2, which have one hydrophobic region and one ATP - binding region each . They assemble into a heterodimer, which results in a four - domain transporter . </P>

Transport of peptides from the cytosol into the endoplasmic reticulum is via