Gla-rich protein (GRP), a new vitamin K-dependent protein identified from sturgeon cartilage and highly conserved in vertebrates. | - CCMAR -

Journal Article

TitleGla-rich protein (GRP), a new vitamin K-dependent protein identified from sturgeon cartilage and highly conserved in vertebrates.
Publication TypeJournal Article
AuthorsViegas, CSB, Simes, DC, Laizé, V, Williamson, MK, Price, PA, M. Cancela, L
Year of Publication2008
JournalJ Biol Chem
Date Published2008 Dec 26
KeywordsAmino Acid Sequence, Animals, Binding Sites, Cartilage, Conserved Sequence, Fish Proteins, Fishes, Gene Expression Regulation, Humans, Hydrogen-Ion Concentration, Models, Biological, Molecular Sequence Data, Phylogeny, Sequence Homology, Amino Acid, Tissue Distribution, Vitamin K

We report the isolation of a novel vitamin K-dependent protein from the calcified cartilage of Adriatic sturgeon (Acipenser nacarii). This 10.2-kDa secreted protein contains 16 gamma-carboxyglutamic acid (Gla) residues in its 74-residue sequence, the highest Gla percent of any known protein, and we have therefore termed it Gla-rich protein (GRP). GRP has a high charge density (36 negative+16 positive=20 net negative) yet is insoluble at neutral pH. GRP has orthologs in all taxonomic groups of vertebrates, and a paralog (GRP2) in bony fish; no GRP homolog was found in invertebrates. There is no significant sequence homology between GRP and the Gla-containing region of any presently known vitamin K-dependent protein. Forty-seven GRP sequences were obtained by a combination of cDNA cloning and comparative genomics: all 47 have a propeptide that contains a gamma-carboxylase recognition site and a mature protein with 14 highly conserved Glu residues, each of them being gamma-carboxylated in sturgeon. The protein sequence of GRP is also highly conserved, with 78% identity between sturgeon and human GRP. Analysis of the corresponding gene structures suggests a highly constrained organization, particularly for exon 4, which encodes the core Gla domain. GRP mRNA is found in virtually all rat and sturgeon tissues examined, with the highest expression in cartilage. Cells expressing GRP include chondrocytes, chondroblasts, osteoblasts, and osteocytes. Because of its potential to bind calcium through Gla residues, we suggest that GRP may regulate calcium in the extracellular environment.


Alternate JournalJ. Biol. Chem.
PubMed ID18836183
PubMed Central IDPMC2605998
Grant ListHL58090 / HL / NHLBI NIH HHS / United States