Human dentin phosphophoryn nucleotide and amino acid sequence

Dentin sialoprotein (DSP) and phosphophoryns (DPP) are major dentin-specifi c non-collagenous proteins and are synthesized by odontoblasts. DPP are ext remely acidic, rich in aspartic acid and serine, possess a high affinity fo r calcium and collagen, and are believed to function in dentin mineralizati on. Whereas DSP and DPP are the products of a single gene in mouse and rat, an analogous human gene has not been described. Using RT-PCR based cloning strategies, we have cloned human DPP cDNA from immature molar root total R NA. The open reading frame of this human DPP cDNA comprises 2364 bp encodin g 788 amino acids rich in serine (58%), aspartic acid (26%) and asparagine (9%). These are mostly arranged as (DSS)(n) (n = 1-16), DS and NSS motifs. The N-terminal sequence (DDP) matches that obtained from human DPP extracte d from the roots of immature teeth. The core protein of this human DPP was calculated to have a molecular weight of 76,906 Da and a net charge of -206 with an isoelectric point of 2.65. Of the serine residues, 53% can potenti ally be phosphorylated by casein kinases I and II. Thus, this newly cloned human cDNA, which encodes a protein with characteristics similar to rat and mouse DPP, is identified as a human DPP.