Seitenhistorie

Bone Morphogenetic Proteins (BMPs) are a family of ligands that belong to the Transforming Growth Factor β (TGFβ) superfamily (Ref). They were originally recognized for their ability to induce endochondral bone formation (Ref).

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Processing

Like all members of the TGFβ superfamily, BMPs are expressed as long precursor proteins, carrying an N-terminal signal peptide, a prodomain and the C-terminal mature peptide. The signal peptide directs the protein to the secretory pathway, while the prodomain mediates proper folding (Ref). BMP monomers are stabilized by a structure known as cystine knot motif: six highly conserved cysteines form three intramolecular disulfide bonds. BMPs are typically secreted as homomeric dimers. Stabilization of the dimer is mediated through an additional cysteine bridge, requiring a seventh cysteine within each monomer (Ref, Ref). Some members of the BMP family, e.g. GDF3 (Ref), GDF9 (Ref), and GDF9B (BMP15; Ref) lack the seventh cysteine. However, they are biologically active and may form non-covalent dimers (Ref). Furthermore, several studies report that BMP heterodimers are more potent than their corresponding homodimers (Ref). The secretion of heterodimers was observed for BMP4/7 (Ref, Ref, Ref), BMP2/5 (Ref), BMP2/6 (Ref), BMP2/7 (Ref), BMP15/GDF9 (Ref), and BMP2b/7 (Ref). Serine endoproteases cleave the proprotein within the trans-Golgi network, producing the mature protein that is subsequently secreted (Ref). For some BMPs, e.g. BMP7 (OP1; Ref) and GDF8 (Myostatin; Ref) the proregion was shown to remain attached to the mature protein even after secretion.

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Table: Binding affinities of BMP family ligands to BMP receptors.

a) BMPs

b) GDFs

Weighing Estimation of binding affinities:
n/a, none, very weak (kD > 1µM), weak (kD 1µM - 100nM), medium (kD 99nM - 50nM), solid (kD 49 -10nM), strong (kD 10nM - 0.5nM), very strong (kD < 0.5nM)

Comment: Please correct the given values!

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Further reading: