PROLINE-RICH GAMMA-CARBOXYGLUTAMIC ACID PROTEIN 1; PRRG1

Alternative titles; symbols

• PROLINE-RICH GLA PROTEIN 1; PRGP1

HGNC Approved Gene Symbol: PRRG1

Cytogenetic location: Xp21.1 Genomic coordinates (GRCh38): X:37,349,363-37,457,290 (from NCBI)

▼ Cloning and Expression
Homologous domains containing 9 to 12 gamma-carboxyglutamic acid (Gla) residues have been identified within the N-terminal 48 amino acids of a number of proteins, including several coagulation and anticoagulation factors. The Gla residues within these Gla domains are produced by the posttranslational modification of specific glutamic acid residues by a vitamin K-dependent gamma-carboxylase (137167) located in the rough endoplasmic reticulum. This reaction requires a gamma-carboxylation recognition sequence contained within a propeptide that is flanked by a signal peptide and the N-terminal domain of the mature protein where the gamma-carboxylation occurs. The coordination of calcium by several Gla residues is required for the proper conformation of the Gla domain. By searching an EST database with an amino acid sequence derived from a highly conserved region of known human Gla domain sequences, Kulman et al. (1997) identified 2 novel Gla domain-containing proteins, PRRG1 and PRRG2 (604429), which they called PRGP1 and PRGP2, respectively. They isolated 4.5- and 1.8-kb full-length cDNAs corresponding to alternatively polyadenylated PRRG1 transcripts containing 3.7- and 0.9-kb 3-prime untranslated regions, respectively. Since Northern blot analysis only detected an approximately 4.6-kb PRRG1 transcript, Kulman et al. (1997) concluded that the longer transcript is the predominant form. The predicted 218-amino acid PRRG1 protein has a 20-amino acid propeptide that contains the highly conserved residues implicated in gamma-carboxylation; an N-terminal Gla domain; a transmembrane region; and a proline-rich C-terminal region that contains PPXY and PXXP motifs, which are found in proteins that interact with WW domains and SH3 domains, respectively. Unlike all other known Gla domain-containing proteins, PRRG1 lacks a discernible signal peptide. The authors stated that PRRG1 is likely oriented with its C terminus in the cytoplasm. Northern blot analysis showed that PRRG1 is expressed in a wide variety of tissues, with the highest expression in spinal cord.

▼ Mapping
Gross (2014) mapped the PRRG1 gene to chromosome Xp21.1 based on an alignment of the PRRG1 sequence (GenBank AF009242) with the genomic sequence (GRCh38).