[7] The TAPBP gene encodes a transmembrane glycoprotein that mediates interaction between newly assembled major histocompatibility complex (MHC) class I molecules and the transporter associated with antigen processing (TAP), which is required for the transport of antigenic peptides across the endoplasmic reticulum membrane.

Tapasin contains a C-terminal double-lysine motif (KKKAE) known to maintain membrane proteins in the endoplasmic reticulum.

In humans, the tapasin gene lies within the major histocompatibility complex on chromosome 6.

[7] Tapasin is a MHC class I antigen-processing molecule present in the lumen of the endoplasmic reticulum.

It plays an important role in the maturation of MHC class I molecules in the ER lumen.