Phosphorylation regulates the secondary structure and function of dentin phosphoprotein peptides.
Dentin phosphoprotein (DPP) is the most acidic protein in vertebrates and structurally is classified as an intrinsically disordered protein. Functionally, DPP is related to dentin and bone formation, however the specifics of such association remain unknown. Here, we used atomistic molecular dynamics simulations to screen selected binding domains of DPP onto hydroxyapatite (HA), which is one of its important interacting partners. From these results, we selected a functionally relevant peptide, Ace-SSDSSDSSDSSDSSD-NH2 (named P5) and its phosphorylated form (named P5P), for experimental characterization. SAXS experiments indicated that in solution P5 was disordered, possibly in an extended conformation while P5P displayed more compact globular conformations. Circular dichroism and FTIR confirmed that, either in the presence or absence of Ca2+/HA, P5 adopts a random coil structure, whereas its phosphorylated counterpart, P5P, has a more compact arrangement associated with conformations that display β-sheet and α-helix motifs when bound to HA. In solution, P5 inhibited HA crystal growth, whereas at similar concentrations, P5P stimulated it. These findings suggest that phosphorylation controls the transient formation of secondary and tertiary structure of DPP peptides, and, most likely of DPP itself, which in turn controls HA growth in solution and possibly HA growth in mineralized tissues.
Mineralized Tissue Research Laboratory, Hospital for Special Surgery, New York, NY, USA; Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA, USA.
Eduardo
E
Villarreal-Ramirez
Department of Biochemistry, Weill Cornell Medical College, New York, NY, USA.
David
D
Eliezer
Instituto de Ciencias Físicas, UNAM, Cuernavaca, Mexico.
Ramon
R
Garduño-Juarez
Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA, USA.
Arne
A
Gericke
IBM Thomas J. Watson Research Center, Yorktown Heights, NY, USA.
Jose Manuel
JM
Perez-Aguilar
Mineralized Tissue Research Laboratory, Hospital for Special Surgery, New York, NY, USA; Department of Physiology, Biophysics and Systems Biology, Weill Cornell Medical College, New York, NY, USA. Electronic address: boskeya@hss.edu.
Adele
A
Boskey
D000595:Amino Acid Sequence; D002113:Calcification, Physiologic; D002942:Circular Dichroism; D017886:Durapatite / Q000737:chemistry; D016326:Extracellular Matrix Proteins / Q000737:chemistry* / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism*; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism*; D010766:Phosphorylation; D017433:Protein Structure, Secondary; D053838:Scattering, Small Angle; D012795:Sialoglycoproteins / Q000737:chemistry* / Q000378:metabolism*; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction; D000099311:Dentin Sialophosphoprotein
D017886:Durapatite; D016326:Extracellular Matrix Proteins; D010455:Peptides; D010750:Phosphoproteins; D012795:Sialoglycoproteins; D000099311:Dentin Sialophosphoprotein
Biomineralization; Dentin phosphoprotein; HA crystal growth; Intrinsically disordered protein; Secondary structure transitions