X-ray crystal structure of bovine 3 Glu-osteocalcin

Vladimir N. Malashkevich, Steven C. Almo, Terry L. Dowd

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

The 3 Glu form of osteocalcin (3 Glu-OCN) is increased in serum during low vitamin K intake or oral anticoagulant use (warfarin). Previous reports using circular dichroism show it is less structured than 3 Gla Ca2+- osteocalcin and does not bind strongly to bone mineral. Recent studies have suggested a role for 3 Glu-OCN as a potential regulator of glucose metabolism. A G-protein-coupled receptor, GPRC6a, found in the pancreas and testes was identified as the putative osteocalcin receptor. The purpose of this study is to determine the high-resolution structure of bovine 3 Glu-OCN, using X-ray crystallography, to understand molecular interactions with mineral and the GPRC6a receptor. Diffraction quality crystals of thermally decarboxylated bovine osteocalcin were grown, and the crystal structure was determined to 1.88 Å resolution. The final refined structure contained residues 17-47 and, like 3 Gla Ca2+-OCN, consisted of three α-helices surrounding a hydrophobic core, a C23-C29 disulfide bond between two of the helices, and no bound Ca2+. Thus, the helical structure of 3 Glu-OCN is Ca 2+-independent but similar to that of 3 Gla Ca2+-OCN. A reduced level of mineral binding could result from a lower number of Ca 2+ coordinating ligands on 3 Glu-OCN. The structure suggests the GPRC6a receptor may respond to helical osteocalcin and will aid in providing molecular mechanistic insight into the role of 3 Glu-OCN in glucose homeostasis.

Original languageEnglish (US)
Pages (from-to)8387-8392
Number of pages6
JournalBiochemistry
Volume52
Issue number47
DOIs
StatePublished - Nov 26 2013

Fingerprint

Osteocalcin
Crystal structure
X-Rays
X rays
Minerals
Glucose
Molecular interactions
Vitamin K
X ray crystallography
X Ray Crystallography
Warfarin
G-Protein-Coupled Receptors
Circular Dichroism
Metabolism
Disulfides
Anticoagulants
Testis
Pancreas
Bone
Homeostasis

ASJC Scopus subject areas

  • Biochemistry

Cite this

X-ray crystal structure of bovine 3 Glu-osteocalcin. / Malashkevich, Vladimir N.; Almo, Steven C.; Dowd, Terry L.

In: Biochemistry, Vol. 52, No. 47, 26.11.2013, p. 8387-8392.

Research output: Contribution to journalArticle

Malashkevich, VN, Almo, SC & Dowd, TL 2013, 'X-ray crystal structure of bovine 3 Glu-osteocalcin', Biochemistry, vol. 52, no. 47, pp. 8387-8392. https://doi.org/10.1021/bi4010254
Malashkevich, Vladimir N. ; Almo, Steven C. ; Dowd, Terry L. / X-ray crystal structure of bovine 3 Glu-osteocalcin. In: Biochemistry. 2013 ; Vol. 52, No. 47. pp. 8387-8392.
@article{dbb96eb217474c409aa445caa09507f4,
title = "X-ray crystal structure of bovine 3 Glu-osteocalcin",
abstract = "The 3 Glu form of osteocalcin (3 Glu-OCN) is increased in serum during low vitamin K intake or oral anticoagulant use (warfarin). Previous reports using circular dichroism show it is less structured than 3 Gla Ca2+- osteocalcin and does not bind strongly to bone mineral. Recent studies have suggested a role for 3 Glu-OCN as a potential regulator of glucose metabolism. A G-protein-coupled receptor, GPRC6a, found in the pancreas and testes was identified as the putative osteocalcin receptor. The purpose of this study is to determine the high-resolution structure of bovine 3 Glu-OCN, using X-ray crystallography, to understand molecular interactions with mineral and the GPRC6a receptor. Diffraction quality crystals of thermally decarboxylated bovine osteocalcin were grown, and the crystal structure was determined to 1.88 {\AA} resolution. The final refined structure contained residues 17-47 and, like 3 Gla Ca2+-OCN, consisted of three α-helices surrounding a hydrophobic core, a C23-C29 disulfide bond between two of the helices, and no bound Ca2+. Thus, the helical structure of 3 Glu-OCN is Ca 2+-independent but similar to that of 3 Gla Ca2+-OCN. A reduced level of mineral binding could result from a lower number of Ca 2+ coordinating ligands on 3 Glu-OCN. The structure suggests the GPRC6a receptor may respond to helical osteocalcin and will aid in providing molecular mechanistic insight into the role of 3 Glu-OCN in glucose homeostasis.",
author = "Malashkevich, {Vladimir N.} and Almo, {Steven C.} and Dowd, {Terry L.}",
year = "2013",
month = "11",
day = "26",
doi = "10.1021/bi4010254",
language = "English (US)",
volume = "52",
pages = "8387--8392",
journal = "Biochemistry",
issn = "0006-2960",
publisher = "American Chemical Society",
number = "47",

}

TY - JOUR

T1 - X-ray crystal structure of bovine 3 Glu-osteocalcin

AU - Malashkevich, Vladimir N.

AU - Almo, Steven C.

AU - Dowd, Terry L.

PY - 2013/11/26

Y1 - 2013/11/26

N2 - The 3 Glu form of osteocalcin (3 Glu-OCN) is increased in serum during low vitamin K intake or oral anticoagulant use (warfarin). Previous reports using circular dichroism show it is less structured than 3 Gla Ca2+- osteocalcin and does not bind strongly to bone mineral. Recent studies have suggested a role for 3 Glu-OCN as a potential regulator of glucose metabolism. A G-protein-coupled receptor, GPRC6a, found in the pancreas and testes was identified as the putative osteocalcin receptor. The purpose of this study is to determine the high-resolution structure of bovine 3 Glu-OCN, using X-ray crystallography, to understand molecular interactions with mineral and the GPRC6a receptor. Diffraction quality crystals of thermally decarboxylated bovine osteocalcin were grown, and the crystal structure was determined to 1.88 Å resolution. The final refined structure contained residues 17-47 and, like 3 Gla Ca2+-OCN, consisted of three α-helices surrounding a hydrophobic core, a C23-C29 disulfide bond between two of the helices, and no bound Ca2+. Thus, the helical structure of 3 Glu-OCN is Ca 2+-independent but similar to that of 3 Gla Ca2+-OCN. A reduced level of mineral binding could result from a lower number of Ca 2+ coordinating ligands on 3 Glu-OCN. The structure suggests the GPRC6a receptor may respond to helical osteocalcin and will aid in providing molecular mechanistic insight into the role of 3 Glu-OCN in glucose homeostasis.

AB - The 3 Glu form of osteocalcin (3 Glu-OCN) is increased in serum during low vitamin K intake or oral anticoagulant use (warfarin). Previous reports using circular dichroism show it is less structured than 3 Gla Ca2+- osteocalcin and does not bind strongly to bone mineral. Recent studies have suggested a role for 3 Glu-OCN as a potential regulator of glucose metabolism. A G-protein-coupled receptor, GPRC6a, found in the pancreas and testes was identified as the putative osteocalcin receptor. The purpose of this study is to determine the high-resolution structure of bovine 3 Glu-OCN, using X-ray crystallography, to understand molecular interactions with mineral and the GPRC6a receptor. Diffraction quality crystals of thermally decarboxylated bovine osteocalcin were grown, and the crystal structure was determined to 1.88 Å resolution. The final refined structure contained residues 17-47 and, like 3 Gla Ca2+-OCN, consisted of three α-helices surrounding a hydrophobic core, a C23-C29 disulfide bond between two of the helices, and no bound Ca2+. Thus, the helical structure of 3 Glu-OCN is Ca 2+-independent but similar to that of 3 Gla Ca2+-OCN. A reduced level of mineral binding could result from a lower number of Ca 2+ coordinating ligands on 3 Glu-OCN. The structure suggests the GPRC6a receptor may respond to helical osteocalcin and will aid in providing molecular mechanistic insight into the role of 3 Glu-OCN in glucose homeostasis.

UR - http://www.scopus.com/inward/record.url?scp=84888601009&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84888601009&partnerID=8YFLogxK

U2 - 10.1021/bi4010254

DO - 10.1021/bi4010254

M3 - Article

C2 - 24138653

AN - SCOPUS:84888601009

VL - 52

SP - 8387

EP - 8392

JO - Biochemistry

JF - Biochemistry

SN - 0006-2960

IS - 47

ER -