BSMAP is a 342 amino acid type-I membrane glycoprotein that localizes to organelle membranes and belongs to the TMEM59 family. Expressed at high levels in brain tissue, BSMAP is thought to play a role in brain function and central nervous system activity. The gene encoding BSMAP maps to human chromosome 19, which consists of over 63 million bases, houses approximately 1,400 genes and is recognized for having the greatest gene density of the human chromosomes. It is the genetic home for a number of immunoglobulin (Ig) superfamily members, including the killer cell and leukocyte Ig-like receptors, a number of ICAMs, the CEACAM and PSG family and Fc receptors (FcRs).