The function of Ensembl gene identifier ENSG00000163216 (SPRR2D, small proline rich protein 2D) is as follows. Cross-linked envelope protein of keratinocytes. It is a keratinocyte protein that first appears in the cell cytosol, but ultimately becomes cross-linked to membrane proteins by transglutaminase. All that results in the formation of an insoluble envelope beneath the plasma membrane.