APLP1 (amyloid precursor-like protein 1) is a protein whose predicted amino acid sequence is 42% identical and 64% similar to that of the amyloid beta protein precursor (APP).APLP2 is a human sperm membrane protein which contains a segment with high homology to the transmembrane-cytoplasmic domains of APP found in brain plaques of Alzheimer disease patients. The human amyloid precursor-like protein APLP2 is a highly conserved homolog of a sequence-specific DNA-binding mouse protein with an important function in the cell cycle.