This protein is produced by a bicistronic gene which also produces the major prion protein/PRNP from an overlapping reading frame. The alternative prion protein and PRNP (AC P23907) have no apparent direct functional relation since a mutation that removes the start codon of the AltPrP has no apparent effect on the biology of PRNP (By similarity). In mouse and hamster, the alternative initiation AUG codon is absent and is replaced by a GUG codon.