Osteopontin binds multiple calcium ions with high affinity and independently of phosphorylation status

Eva Kläning; Brian Christensen; Esben Skipper Sørensen; Thomas Vorup-Jensen; Jan K Jensen

doi:10.1016/j.bone.2014.05.020

Osteopontin binds multiple calcium ions with high affinity and independently of phosphorylation status

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaper › Journal article › Research › peer-review

65 Citations (Scopus)

Abstract

Osteopontin (OPN) is an acidic, intrinsically disordered extracellular matrix protein with a capacity to modulate biomineralization in vitro and in vivo. The role of posttranslational modification of osteopontin has been intensively studied. Phosphorylation of OPN has been demonstrated to play a role in inhibition of biomineral formation and growth in vitro. Here, we used isothermal titration calorimetry (ITC) to investigate the ability of OPN to bind the divalent cations Ca(2+) and Mg(2+), both essential components of inorganic minerals in vivo. We found, that bovine OPN binds ~10 Ca(2+) ions with an apparent affinity ~50-fold tighter than Mg(2+), both regardless of OPN phosphorylation, and with affinities significantly stronger than previously reported. These results were confirmed using human derived OPN. This implies that a majority of the acidic residues within OPN must be engaged in calcium interaction under physiological conditions.

Original language	English
Journal	Bone
Volume	66
Pages (from-to)	90-95
Number of pages	6
ISSN	8756-3282
DOIs	https://doi.org/10.1016/j.bone.2014.05.020
Publication status	Published - Sept 2014

Access to Document

10.1016/j.bone.2014.05.020

Library access?

Check availability with the Royal Danish Library

Cite this

@article{863a13f85f9b48f2bba30d4142794a3f,

title = "Osteopontin binds multiple calcium ions with high affinity and independently of phosphorylation status",

abstract = "Osteopontin (OPN) is an acidic, intrinsically disordered extracellular matrix protein with a capacity to modulate biomineralization in vitro and in vivo. The role of posttranslational modification of osteopontin has been intensively studied. Phosphorylation of OPN has been demonstrated to play a role in inhibition of biomineral formation and growth in vitro. Here, we used isothermal titration calorimetry (ITC) to investigate the ability of OPN to bind the divalent cations Ca(2+) and Mg(2+), both essential components of inorganic minerals in vivo. We found, that bovine OPN binds \textasciitilde{}10 Ca(2+) ions with an apparent affinity \textasciitilde{}50-fold tighter than Mg(2+), both regardless of OPN phosphorylation, and with affinities significantly stronger than previously reported. These results were confirmed using human derived OPN. This implies that a majority of the acidic residues within OPN must be engaged in calcium interaction under physiological conditions.",

author = "Eva Kl{\"a}ning and Brian Christensen and S{\o}rensen, \{Esben Skipper\} and Thomas Vorup-Jensen and Jensen, \{Jan K\}",

year = "2014",

month = sep,

doi = "10.1016/j.bone.2014.05.020",

language = "English",

volume = "66",

pages = "90--95",

journal = "Bone",

issn = "8756-3282",

publisher = "Elsevier Inc.",

}

TY - JOUR

T1 - Osteopontin binds multiple calcium ions with high affinity and independently of phosphorylation status

AU - Kläning, Eva

AU - Christensen, Brian

AU - Sørensen, Esben Skipper

AU - Vorup-Jensen, Thomas

AU - Jensen, Jan K

PY - 2014/9

Y1 - 2014/9

N2 - Osteopontin (OPN) is an acidic, intrinsically disordered extracellular matrix protein with a capacity to modulate biomineralization in vitro and in vivo. The role of posttranslational modification of osteopontin has been intensively studied. Phosphorylation of OPN has been demonstrated to play a role in inhibition of biomineral formation and growth in vitro. Here, we used isothermal titration calorimetry (ITC) to investigate the ability of OPN to bind the divalent cations Ca(2+) and Mg(2+), both essential components of inorganic minerals in vivo. We found, that bovine OPN binds ~10 Ca(2+) ions with an apparent affinity ~50-fold tighter than Mg(2+), both regardless of OPN phosphorylation, and with affinities significantly stronger than previously reported. These results were confirmed using human derived OPN. This implies that a majority of the acidic residues within OPN must be engaged in calcium interaction under physiological conditions.

AB - Osteopontin (OPN) is an acidic, intrinsically disordered extracellular matrix protein with a capacity to modulate biomineralization in vitro and in vivo. The role of posttranslational modification of osteopontin has been intensively studied. Phosphorylation of OPN has been demonstrated to play a role in inhibition of biomineral formation and growth in vitro. Here, we used isothermal titration calorimetry (ITC) to investigate the ability of OPN to bind the divalent cations Ca(2+) and Mg(2+), both essential components of inorganic minerals in vivo. We found, that bovine OPN binds ~10 Ca(2+) ions with an apparent affinity ~50-fold tighter than Mg(2+), both regardless of OPN phosphorylation, and with affinities significantly stronger than previously reported. These results were confirmed using human derived OPN. This implies that a majority of the acidic residues within OPN must be engaged in calcium interaction under physiological conditions.

U2 - 10.1016/j.bone.2014.05.020

DO - 10.1016/j.bone.2014.05.020

M3 - Journal article

C2 - 24928493

SN - 8756-3282

VL - 66

SP - 90

EP - 95

JO - Bone

JF - Bone

ER -

Osteopontin binds multiple calcium ions with high affinity and independently of phosphorylation status

Abstract

Access to Document

Library access?

Fingerprint

Cite this