title: A mass spectrometric study of metal binding to osteocalcin.
abstract: Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry was used to investigate Ca(2+), Mg(2+), and La(3+) binding to bovine bone osteocalcin (OCN). OCN was shown to bind 3 mol Ca(2+) per mol protein. There was also evidence for the presence of four additional metal binding sites. Ca(2+) increased the formation of the OCN dimer. Mg(2+) bound to OCN to the same extent as Ca(2+) but did not induce the dimerization of OCN. La(3+) bound to a lesser extent than either Ca(2+) or Mg(2+) to OCN and, like Mg(2+), did not influence dimerization. Each Gla residue of OCN participates in Ca(2+) binding, whereas Mg(2+) binding may occur preferentially at sites other than Gla residues. This implies that the different natures of Ca(2+)- and Mg(2+)-containing OCN complexes influence the tendency of OCN to form a dimer.
authors.affiliation: Department of Chemistry, University of Joensuu, Post Office Box 111, FIN-80101 Joensuu, Finland.
authors.forename: Marjaana
authors.initials: M
authors.lastname: Nousiainen
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Derrick
authors.forename: Mari T
authors.initials: MT
authors.lastname: Kaartinen
authors.forename: Pekka H
authors.initials: PH
authors.lastname: Mäenpää
authors.forename: Juha
authors.initials: J
authors.lastname: Rouvinen
authors.forename: Pirjo
authors.initials: P
authors.lastname: Vainiotalo
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D017357:Cyclotrons; D019281:Dimerization; D007811:Lanthanum / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism*; D008969:Molecular Sequence Data; D015675:Osteocalcin / Q000378:metabolism*; D011485:Protein Binding; D021241:Spectrometry, Mass, Electrospray Ionization; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D015675:Osteocalcin; D007811:Lanthanum; D008274:Magnesium; D002118:Calcium