PDBsum entry 2ft3

Structural protein, signaling protein

PDB id: 2ft3

Contents

Protein chains

(+ 0 more) 303 a.a. *

Ligands

NAG ×6

FLC ×6

* Residue conservation analysis

PDB id:

2ft3

Name:

Structural protein, signaling protein

Title:

Crystal structure of the biglycan dimer core protein

Structure:

Biglycan. Chain: a, b, c, d, e, f. Fragment: residues 38-369. Synonym: bone/cartilage proteoglycan i, pg-s1, leucine-rich pg i

Source:

Bos taurus. Cattle. Organism_taxid: 9913. Tissue: extracted from articular cartilage

Biol. unit:

Dimer (from PQS)

Resolution:

3.40Å R-factor: 0.259 R-free: 0.291

Authors:

P.G.Scott,C.M.Dodd,E.M.Bergmann

Key ref:

P.G.Scott et al. (2006). Crystal structure of the biglycan dimer and evidence that dimerization is essential for folding and stability of class I small leucine-rich repeat proteoglycans. J Biol Chem, 281, 13324-13332. PubMed id: 16547006 DOI: 10.1074/jbc.M513470200

Date:

23-Jan-06 Release date: 28-Mar-06

Protein chains

P21809  (PGS1_BOVIN) -  Biglycan from Bos taurus

Seq: 369 a.a.

Struc: 303 a.a.

DOI no: 10.1074/jbc.M513470200

J Biol Chem 281:13324-13332 (2006)

PubMed id: 16547006

Crystal structure of the biglycan dimer and evidence that dimerization is essential for folding and stability of class I small leucine-rich repeat proteoglycans.

P.G.Scott, C.M.Dodd, E.M.Bergmann, J.K.Sheehan, P.N.Bishop.

ABSTRACT

Biglycan and decorin are two closely related proteoglycans whose protein cores contain leucine-rich repeats flanked by disulfides. We have previously shown that decorin is dimeric both in solution and in crystal structures. In this study we determined whether biglycan dimerizes and investigated the role of dimerization in the folding and stability of these proteoglycans. We used light scattering to show that biglycan is dimeric in solution and solved the crystal structure of the glycoprotein core of biglycan at 3.40-angstroms resolution. This structure reveals that biglycan dimerizes in the same way as decorin, i.e. by apposition of the concave inner surfaces of the leucine-rich repeat domains. We demonstrate that low concentrations of guanidinium chloride denature biglycan and decorin but that the denaturation is completely reversible following removal of the guanidinium chloride, as assessed by circular dichroism spectroscopy. Furthermore, the rate of refolding is dependent on protein concentration, demonstrating that it is not a unimolecular process. Upon heating, decorin shows a single structural transition at a T(m) of 45-46 degrees C but refolds completely upon cooling to 25 degrees C. This property of decorin enabled us to show both by calorimetry and light scattering that dimer to monomer transition coincided with unfolding and monomer to dimer transition coincided with refolding; thus these processes are inextricably linked. We further conclude that folded monomeric biglycan or decorin cannot exist in solution. This implies novel interrelated functions for the parallel beta sheet faces of these leucine-rich repeat proteoglycans, including dimerization and stabilization of protein folding.

Selected figure(s)

Figure 2.
FIGURE 2. A, schematic representation of the structure of the biglycan monomer. Strands are colored yellow, helices red, and other secondary structures green. B, overlay of C- atoms of biglycan (green) and decorin (red) dimers. Structures were overlaid in Xfit (McRee (36)). C, wall-eyed stereo view of calculated electron density (2mF[o] - DF[c], contoured at 1.5 ) around the near N-terminal disulfide knot in biglycan, showing cysteine residues 27 linked to 33 and 31 linked to 40. D, calculated electron density (2mF[o] - DF[c], contoured at 1.5 ) around citrate ion, together with the surfaces of nearby residues. Electron densities were calculated using CNS version 1.1 (Brünger et al. (35)). All figures were generated using PYMOL version 0.97 (pymol.sourceforge.net/).

Figure 5.
FIGURE 5. Refolding of GdnHCl-denatured decorin (A) and biglycan (B), monitored by CD. Protein concentrations (expressed as monomer) were 2.92 µM (squares) and 0.77 µM (triangles) for decorin and 2.57 µM (squares) and 0.83 µM (triangles) for biglycan.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2006, 281, 13324-13332) copyright 2006.

Figures were selected by the author.