Teleost fish osteocalcin 1 and 2 share the ability to bind the calcium mineral phase
The occurrence of a second osteocalcin (OC2) has been reported in teleost fish, where it coexists with OC1 in some species. While it has been proposed that OC2 gene originated from OC1 through the fish whole-genome duplication event, little information is available on its molecular function and physiological role. The present study brings biological data supporting the presence of OC2 in the mineral phase of teleost fish bone and its association with the mineral phase together with OC1. The occurrence of OC2 forms with different levels of phosphorylation or γ-carboxylation, and with amino acid substitutions was observed. Comparative analysis of mature peptide sequences revealed the high conservation existing between OC1 and OC2, in particular within the core γ-carboxyglutamic acid domain, and suggests that both protein forms may have the same function, i.e., binding of calcium ions or hydroxyapatite crystals.
KeywordsOsteocalcin Vitamin K-dependent proteins Protein purification Bone tissue Teleost fish
This work was supported by Grants POCTI/MAR/57921/2004 and PTDC/MAR/105152/2008 from the Portuguese Science and Technology Foundation (including funds from FEDER and OE) and by CCMAR funding. The authors are grateful to Dr. P. Gavaia for Senegalese sole OC2 partial cDNA sequence. S. Cavaco, J. Rosa and V. Roberto were the recipients of PhD fellowships SFRH/BD/60867/2009, SFRH/BD/47433/2008 and SFRH/BD/38607/2007, respectively, from the Portuguese Science and Technology Foundation.
- Lie KK, Moren M (2012) Retinoic acid induces two osteocalcin isoforms and inhibits markers of osteoclast activity in Atlantic cod (Gadus morhua) ex vivo cultured craniofacial tissues. Comp Biochem Physiol A: Mol Integr Physiol 161:174–184Google Scholar
- Renn J, Winkler C (2010) Characterization of collagen type 10a1 and osteocalcin in early and mature osteoblasts during skeleton formation in medaka. J Appl Ichthyol 26:196–201Google Scholar
- Simes DC, Williamson MK, Ortiz-Delgado JB, Viegas CSB, Price PA, Cancela ML (2003) Purification of matrix Gla protein (MGP) from a marine teleost fish, Argyrosomus regius: calcified cartilage and not bone as the primary site of MGP accumulation in fish. J Bone Miner Res 18:244–259PubMedGoogle Scholar