PRRG3 (proline-rich gamma-carboxyglutamic acid protein 3), also known as TMG3 (transmembrane gamma-carboxyglutamic acid protein 3) or PRGP3, is a 231 amino acid single-pass type I membrane protein found in kidney, heart and brain. PRRG3 contains an N-terminal Gla (gamma-carboxy-glutamate) domain, two PPXY motifs and is encoded by a gene that maps to human chromosome Xq28. Chromosome X consists of about 153 million base pairs and nearly 1,000 genes. Color blindness, hemophilia and Duchenne muscular dystrophy are well known X chromosome-linked conditions which affect males more frequently, as males carry a single X chromosome.